Copyright is a collection of divisible, exclusive and limited rights associated with creative expression. These rights include copying, public performance, public display, distribution, and the creation of derivative works. There are exemptions to copyright, such as fair use, first sale (the exemption libraries and others can lend materials), educational uses and specific library and archival exemptions.
To be eligible for copyright protection, an object must be fixed in a tangible form (which includes digital formats) and it must possess at least a minimal amount of creativity. Facts cannot be copyrighted, although the selection and arrangement of facts may be copyrighted.
Copyright in a work generally belongs to the person who created or fixed the work in tangible form, with some exceptions such as work for hire. Any of the rights associated with copyright can be transferred in writing. For example, a person can sell the right to publish their book in print to a publisher. Copyright holders can also license their works. The Gnu Public License and the Creative Commons licenses are examples of copyright licenses.
In the US
In the United States, most copyright law is reflected in Federal law.
Copyright in the U.S. has a Constitutional basis: To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries; -U.S. CONST., art. I, § 8, cl. 8. Copyright is ultimately intended to benefit the public by providing an economic incentive to creators. Copyright is often viewed as a balance between the interests of the creators and the interests of the public.
The expanding duration of copyright protection has been a source of some debate (e.g., the Sonny Bono Copyright Term Extension Act), as have recent laws which ban copyright circumvention (e.g., the Digital Millennium Copyright Act) and broaden the scope of what can be copyrighted (e.g., the proposed Database and Collections of Information Misappropriation Act).
Content providers often exaggerate the copyright protections afforded to them. For example, to hear Major League Baseball tell it, you can't tell your neighbor the score of last night's baseball game without expressed written consent to reproduce an account of it. Some dire publishers' warnings about copying materials may be as equally exaggerated.
The United States Copyright Office operates under the auspices of the Library of Congress.