For Wikipedia policy about copyright issues, see Wikipedia:Copyrights
Copyright is a set of exclusive rights regulating the use of a particular expression of an idea or information. At its most general, it is literally "the right to copy" an original creation. In most cases, these rights are of limited duration. The symbol for copyright is ©, and in some jurisdictions may alternatively be written as either (c) or (C).
Copyright may subsist in a wide range of creative, intellectual, or artistic forms or "works". These include poems, theses, plays, and other literary works, movies, choreographic works (dances, ballets, etc.), musical compositions, audio recordings, paintings, drawings, sculptures, photographs, software, radio and television broadcasts of live and other performances, and, in some jurisdictions, industrial designs. Designs or industrial designs may have separate or overlapping laws applied to them in some jurisdictions. Copyright is one of the laws covered by the umbrella term intellectual property.
Copyright law covers only the form or manner in which ideas or information have been manifested, the "form of material expression". It is not designed or intended to cover the actual idea, concepts, facts, styles, or techniques which may be embodied in or represented by the copyright work. For example, the copyright which subsists in relation to a Mickey Mouse cartoon prohibits unauthorized parties from distributing copies of the cartoon or creating derivative works which copy or mimic Disney's particular anthropomorphic mouse, but does not prohibit the creation of artistic works about anthropomorphic mice in general, so long as they are sufficiently different to not be deemed imitative of the original. In some jurisdictions, copyright law provides scope for satirical or interpretive works which themselves may be copyrighted. Other laws may impose legal restrictions on reproduction or use where copyright does not - such as trademarks and patents.
Copyright laws are standardized through international conventions such as the Berne Convention in some countries and are required by international organizations such as European Union or World Trade Organization from their member states.

Copyright
Patents
Trademarks
Geographical indication
Industrial design rights
Trade secrets
Related rights
Tradenames
Domain names
Database rights
Mask work
Plant breeders' rights
Supplementary protection certificate
Traditional knowledge History
The 1886 Berne Convention first established recognition of copyrights among sovereign nations, rather than merely bilaterally. Under the Berne Convention, copyrights for creative works do not have to be asserted or declared, as they are automatically in force at creation: an author need not "register" or "apply for" a copyright in countries adhering to the Berne Convention. As soon as a work is "fixed", that is, written or recorded on some physical medium, its author is automatically entitled to all copyrights in the work, and to any derivative works unless and until the author explicitly disclaims them, or until the copyright expires. The Berne Convention also resulted in foreign authors being treated equivalently to domestic authors, in any country signed onto the Convention.
The UK signed the Berne Convention in 1887 but did not implement large parts of it until 100 years later with the passage of the Copyright, Designs and Patents Act of 1988. The USA did not sign the Berne Convention until 1989.
The regulations of the Berne Convention are incorporated into the World Trade Organization's TRIPS agreement, thus making the Berne Convention practically world-wide.

The Berne Convention
Typically, a work must meet minimal standards of originality in order to qualify for copyright, and the copyright expires after a set period of time (some jurisdictions may allow this to be extended). Different countries impose different tests, although generally the requirements are low; in the United Kingdom there has to be some 'skill, originality and work' which has gone into it. However, even fairly trivial amounts of these qualities are sufficient for determining whether a particular act of copying constitutes an infringement of the author's original expression. In Australia and the United Kingdom it has been held that a single word is insufficient to comprise a copyright work. In the UK, however, single words or a string of words, usually less than eight, can be registered as a "Trade Mark" instead.
In the United States, copyright has been made automatic (in the style of the Berne Convention) since March 1, 1989, which has had the effect of making it appear to be more like a property right. Thus, as with some forms of personal property, a copyright need not be granted or obtained through official registration with any government office. Once an idea has been reduced to tangible form, for example by securing it in a fixed medium (such as a drawing, sheet music, photograph, a videotape or a letter), the copyright holder is entitled to enforce his or her exclusive rights. However, while a copyright need not be officially registered for the copyright owner to begin exercising his exclusive rights, registration of works (where the laws of that jurisdiction provide for registration) does have benefits; it serves as prima facie evidence of a valid copyright and enables the copyright holder to seek statutory damages and attorney's fees (whereas in the USA, for instance, registering after an infringement only enables one to receive actual damages and lost profits). The original holder of the copyright may be the employer of the actual author rather than the author himself if the work is a "work for hire". Again, this principle is widespread; in English law the Copyright Designs and Patents Act 1988 provides that where a work in which copyright subsists is made by an employee in the course of that employment, the copyright is automatically owned by the employer which would be a "Work for Hire."
Copyrights are generally enforced by the holder in a civil law court, but there are also criminal infringement statutes. Criminal sanctions are generally aimed at serious counterfeiting activity, but are now becoming more commonplace as copyright collectives such as the RIAA are, more and more, targeting the file sharing home Internet user. Thus far, however, most such cases against file sharers have been settled out of court for several thousands dollars. (See: File sharing and the law)

Obtaining and enforcing copyright
Use of a copyright notice — consisting of the letter C inside of a circle (that is, "©"), the abbreviation "Copr.", or the word "Copyright", followed by the year of the first publication of the work and the name of the copyright holder — was part of previous United States statutory requirements. (Note that the letter C inside of parentheses ("(c)") has never been an officially recognized designator.) The proper Copyright notice for audio recordings of musical compositions is a "P" inside a circle which stands for Phonorecord. But in 1989, the U.S. enacted the Berne Convention Implementation Act, amending the 1976 Copyright Act to conform to most of the provisions of the Berne Convention. As a result, the use of copyright notices has become optional to claim copyright, because the Berne Convention makes copyright automatic.[1] However, notice of copyright (using these marks) does have consequences in terms of allowable damages in an infringement lawsuit in some places.
It is important to understand that absence of the copyright symbol does not mean that the work is not covered by copyright. The work once created from originality through 'mental labor' is instantaneously considered copyrighted to that person. Thus, a natural copyright exists from the time a work is invented or created regardless of whether a work has been registered with the U.S. Copyright Office. Since all countries have separate copyright laws, there is no such thing as an International Copyright. The Berne Convention, however, makes the copyright automatic as well. Should Copyright Infringement litigation ensue, registration with the U.S. Copyright Office is highly suggested if one is to prevail in court.
The phrase All rights reserved was once a necessary formal notice that all rights granted under existing copyright law are retained by the copyright holder and that legal action may be taken against copyright infringement. It was provided as a result of the Buenos Aires Convention of 1910, which required some statement of reservation of rights to grant international coverage in all the countries that were signatory to that convention. While it is commonplace to see it, this notice is now superfluous, as every country that is a member of the Buenos Aires Convention is also a member of the Berne Convention, which hold a copyright to be valid in all signatory states without any formality of notice.
This phrase is sometimes still used even on some documents to which the original author does not retain all rights granted by copyright law, such as works released under a copyleft license. It is, however, only a habitual formality and is unlikely to have legal consequences.

Copyright notices
Several exclusive rights typically attach to the holder of a copyright:
The phrase "exclusive right" means that only the copyright holder is free to exercise the attendant rights, and others are prohibited using the work without the consent of the copyright holder. Copyright is often called a "negative right", as it serves to prohibit people (e.g. readers, viewers, or listeners, and primarily publishers and would be publishers) from doing something, rather than permitting people (e.g. authors) to do something. In this way it is similar to the unregistered design right in English law and European law. The rights of the copyright holder also permit him/her to not use or exploit their copyright for its duration. This means an author can choose to exploit their copyright for some of the duration and then not for the rest, vice versa, or entirely one or the other.
There is however a critique which rejects this assertion as being based on a philosophical interpretation of copyright law, and is not universally shared. There is also debate on whether copyright should be considered a property right or a moral right. Many argue that copyright does not exist merely to restrict third parties from publishing ideas and information, and that defining copyright purely as a negative right is incompatible with the public policy objective of encouraging authors to create new works and enrich the public domain.
The right to adapt a work means to transform the way in which the work is expressed. Examples include developing a stage play or film script from a novel; translating a short story; and making a new arrangement of a musical work.

to produce copies or reproductions of the work and to sell those copies (including, typically, electronic copies)
to import or export the work
to create derivative works (works that adapt the original work)
to perform or display the work publicly
to sell or assign these rights to others
to transmit or display by means of digital audio transmission (XM Satellite Radio, Sirius) Exclusive rights

Main article: Limitations and exceptions to copyright Limits and exceptions to copyright

Main article: Idea-expression divide The first-sale doctrine and exhaustion of rights

Main articles: Fair use and Fair dealing Fair use and fair dealing
A copyright, or aspects of it, may be assigned or transferred from one party to another. For example, a musician who records an album will often sign an agreement with a record company in which the musician agrees to transfer all copyright in the recordings in exchange for royalties and other considerations. The creator (and original copyright holder) benefits, or expects to, from production and marketing capabilities far beyond those of the author. In the digital age of music, music may be copied and distributed at minimal cost through the Internet, however the record industry attempts to provide promotion and marketing for the artist and his work so it can reach a much larger audience. A copyright holder need not transfer all rights completely, though many publishers will insist. Some of the rights may be transferred, or else the copyright holder may grant another party a non-exclusive license to copy and/or distribute the work in a particular region or for a specified period of time. A transfer or licence may have to meet particular formal requirements in order to be effective; see section 239 of the Australia Copyright Act 1968 (Cth). Under Australian law, it is not enough to pay for a work to be created in order to also own the copyright. The copyright itself must be expressly transferred in writing.
Under the U.S. Copyright Act, a transfer of ownership in copyright must be memorialized in a writing signed by the transferor. For that purpose, ownership in copyright includes exclusive licenses of rights. Thus exclusive licenses, to be effective, must be granted in a written instrument signed by the grantor. No special form of transfer or grant is required. A simple document that identifies the work involved and the rights being granted is sufficient. Non-exclusive grants (often called non-exclusive licenses) need not be in writing under U.S. law. They can be oral or even implied by the behavior of the parties. Transfers of copyright ownership, including exclusive licenses, may and should be recorded in the U.S. Copyright Office. (Information on recording transfers is available on the Office's web site.) While recording is not required to make the grant effective, it offers important benefits, much like those obtained by recording a deed in a real estate transaction.
Copyright may also be licensed. Some jurisdictions may provide that certain classes of copyrighted works be made available under a prescribed statutory license (e.g. musical works in the United States used for radio broadcast or performance). This is also called a compulsory license, because under this scheme, anyone who wishes to copy a covered work does not need the permission of the copyright holder, but instead merely files the proper notice and pays a set fee established by statute (or by an agency decision under statutory guidance) for every copy made. Failure to follow the proper procedures would place the copier at risk of an infringement suit. Because of the difficulty of following every individual work, copyright collectives or collecting societies and performing rights organizations (such as ASCAP, BMI, RIAA and MPAA) have been formed to collect royalties for hundreds (thousands and more) works at once. Though this market solution bypasses the statutory license, the availability of the statutory fee still helps dictate the price per work collective rights organizations charge, driving it down to what avoidance of procedural hassle would justify.

Transfer and licensing
Copyright law covers the creative or artistic expression of an idea. Patent law covers inventions. Trademark law covers distinctive signs which are used in relation to products or services as indicators of origin, as does (in a similar fashion), Trade dress. Registered designs law covers the look or appearance of a manufactured or functional article. Trade secret law covers secret or sensitive knowledge or information.
Although copyright and trademark laws are theoretically distinct, more than one type of them may cover the same item or subject matter. For example, in the case of the Mickey Mouse cartoon, the image and name of Mickey Mouse would be the subject of trademark legislation, while the cartoon itself would be subject to copyright. Titles and character names from books or movies may also be trademarked while the works from which they are drawn may qualify for copyright.
Another point of distinction is that a copyright (and a patent) is generally subject to a statutorily-determined term, whereas a trademark registration may remain in force indefinitely if the trademark is periodically used and renewal fees continue to be duly paid to the relevant jurisdiction's trade marks office or registry. Once the term of a copyright has expired, the formerly copyrighted work enters the public domain and may be freely used or exploited by anyone. Courts in the United States and the United Kingdom have rejected the doctrine of a common law copyright. Public domain works should not be confused with works that are publicly available. Works posted in the internet for example, are publicly available, but are not generally in the public domain. Copying such works may therefore violate the author's copyright.

Similar legal rights
If a pictorial, graphic or sculptural work is a useful article, it is copyrighted only if its aesthetic features are separable from its utilitarian features. A useful article is an article having an intrinsic utilitarian function that is not merely to portray the appearance of the article or to convey information. The must be separable from the functional aspect to be copyrighted.
There are two primary approaches to the separability issue: physical separability and conceptual separability. Physical separability is the ability to take the aesthetic thing away from the functional thing. Conceptual separability can be found in several different ways. It may be present if the useful article is also shown to be appreciated for its aesthetic appeal or by the design approach, which is the idea that separability is only available if the designer is able to make the aesthetic choices that are unaffected by the functional considerations. A question may also be asked of whether an individual would think of the aesthetic aspects of the work being separate from the functional aspects.
There are several different tests available for conceptual separability. The first, the Primary Use test, asks how is the thing primarily used: art or function? The second, the Marketable as Art test, asks can the article be sold as art, whether functional or not. This test does not have much backing, as almost anything can be sold as art. The third test, Temporal Displacement, asks could an individual conceptualize the article as art without conceptualizing functionality at the same time. Finally, the Denicola test says that copyrightability should ultimately depend on the extent to which the work reflects the artistic expression inhibited by functional consideration. If something came to have a pleasing shape because there were functional considerations, the artistic aspect was constrained by those concerns.

Useful articles
Copyright subsists for a variety of lengths in different jurisdictions, with different categories of works and the length it subsists for also depends on whether a work is published or unpublished. In most of the world the default length of copyright for many works is generally the life of the author plus either 50 or 70 years. Copyright in general always expires at the end of the year concerned, rather than on the exact date of the death of the author. (The right to reclaim a copyright--or "terminate the transfer" of a copyright--commences and ends on the anniversaries of exact dates in the United States.)
So when can one conclude that a book is in the public domain? In the United States, all books and other works published before 1923 have expired copyrights and are in the public domain. In addition, works published before 1964 that did not have their copyrights renewed 28 years after first publication year also are in the public domain, except that books originally published outside the US by non-Americans are exempt from this requirement, if they are still under copyright in their home country (see How Can I Tell Whether a Copyright Was Renewed for more details).
Under § 105[2] of the Copyright Act, all works created by the U.S. Government (other than works of standard reference data produced by the U.S. Secretary of Commerce under the Standard Reference Data Act, codified at 15 U.S.C. § 290e[3]) are not subject to copyright. Note, however, that the U.S. Postal Service is a quasi-public corporation wholly owned by the U.S. Government[4], and is not part of the U.S. government, per se. Therefore, works of the Postal Service are not "works of the U.S. government" for purposes of § 105 and are generally subject to copyright. See the Compendium II: Copyright Office Practices, § 206.02(b)[5].
But if the intended exploitation of the work includes publication (or distribution of derivative work, such as a film based on a book protected by copyright) outside the U.S., the terms of copyright around the world must be considered. If the author has been dead more than 70 years, the work is in the public domain in most, but not all, countries. In Italy and France, there are wartime extensions that could increase the term by approximately 6 years in Italy and up to about 14 in France. Some works are covered by copyright in Spain for 80 years after the author's death.
As a curiosity, the famous work Peter Pan has a very complex story of copyright expiry.

How long copyright lasts
In the United States, the Copyright Office maintains that typeface designs are not covered by copyright, and it will not accept applications for their registration. See 37. C.F.R. § 202.1(e). However, if a design is novel and "non-obvious," it may be covered by design patent. See, for example, U.S. Des. Patent No. 289,773 , May 12, 1987), Charles A. Bigelow and Kris A. Holmes, inventors. Germany (in 1981) passed a special extension (Schriftzeichengesetz) to the design patent law (Geschmacksmustergesetz) for protecting them. This permits typefaces being registered as designs in Germany, too.
The United Kingdom (in 1989) has passed a law making typeface designs copyrightable. The British law also applies to designs produced before 1989.

Typefaces

Alternative Compensation System
Compulsory license
Copying
Copyleft
Copyright education
Copyright infringement
Copyright infringement of software
Copyright on the content of patents
Copyright on religious works
Digital rights management
Digital watermarking
File sharing and the law
Freedom of panorama
Glossary of legal terms in technology
List of copyright treaty membership
List of leading legal cases in copyright law
List of countries' copyright length
Moral rights
Paracopyright
Production music
Public domain
Reproduction fees
Rent-seeking
Software copyright
Copyright levies
Threshold pledge system See also

Australian copyright law
Canadian copyright law
Copyright law in the People's Republic of China
Copyright law of the European Union
Dutch copyright law (The Netherlands)
French copyright law, which is based on another philosophy, not founded on "copyright" but on the "Right of the Author" (droit d'auteur).
German copyright law
Hong Kong copyright law
Japan copyright law
Jordanian copyright law
Philippine copyright law
Russian copyright law
Spanish copyright law
Copyright law of Switzerland
Copyright law of the United Kingdom
United States copyright law National copyright laws

Berne Convention for the Protection of Literary and Artistic Works of 1886
Universal Copyright Convention of 1952
Rome Convention of 1961
The WTO Agreement on Trade-Related Aspects of Intellectual Property Rights (TRIPS), of 1994
WIPO Copyright Treaty of 1996
WIPO Performances and Phonograms Treaty of 1996 International treaties

Anti-copyright
Copyleft
Copynorm
Copyright-free
Creative Commons
Crypto-anarchism
Free Culture: How Big Media Uses Technology and the Law to Lock Down Culture and Control Creativity by Lawrence Lessig
Opposition to copyright
Permission culture — neologism by Lawrence Lessig.
The Uneasy Case for Copyright: A Study of Copyright in Books, Photocopies, and Computer Programs by Stephen Breyer. Critique

The Disneyland Memorial Orgy Other

Digital Millennium Copyright Act (US)
Sonny Bono Copyright Term Extension Act (US)
EU Copyright Directive
Directive on harmonizing the term of copyright protection (EU) Some legislation

Further reading

China Law Blog Frequent commentary on China IP laws, including copyright China

Copyright Act of (South) Korea South Korea

[6] (In Spanish). Mexico

Law on Computer Software (Unofficial translation)
Law on Industrial Design (Unofficial translation)
Law on Invention (Unofficial translation)
Law on Trademark (Unofficial translation)
Law on Copyright (Unofficial translation)
Law on the Place of Origin (Unofficial translation) Russia

Lehman, Bruce: Intellectual Property and the National Information Infrastructure (Report of the Working Group on Intellectual Property Rights, 1995)
Gantz, John & Rochester, Jack B. (2005). Pirates of the Digital Millennium. Financial Times Prentice Hall. ISBN O-13-146315-2. 
Lindsey, Marc: Copyright Law on Campus. Washington State University Press, 2003. ISBN 978-0-87422-264-7.
Mazzone, Jason. Copyfraud. http://ssrn.com/abstract=787244
Moores, Simon - "March of the Spiders:" Policy Challenges for Copyright in the Digital Publishing Environment (2005)
Nimmer, Melville; David Nimmer (1997). Nimmer on Copyright. Matthew Bender. ISBN 0-8205-1465-9. 
Ghosemajumder, Shuman. Advanced Peer-Based Technology Business Models. MIT Sloan School of Management, 2002.
Silverthorne, Sean. Music Downloads: Pirates- or Customers?. Harvard Business School Working Knowledge, 2004.
Steinberg, S.H. & Trevitt, John (1996). Five Hundred Years of Printing, 4th ed., London and New Castle: The British Library and Oak Knoll Press. ISBN 1-884718-19-1. 
Dowd, Raymond J. (2006). Copyright Litigation Handbook, 1st ed., Thomson West. ISBN 0314962794. 
Lyman Ray Patterson (1968). Copyright in Historical Perspective. Vanderbilt University Press. ISBN 0826513735. 
Pievatolo, Maria Chiara. Publicness and Private Intellectual Property in Kant's Political Thought. http://bfp.sp.unipi.it/~pievatolo/lm/kantbraz.html