What is fair use?
The Copyright Act gives copyright holders the exclusive right to reproduce works for a limited time period. Fair use is a limitation on this right. Fair use allows people other than the copyright owner to copy part or, in some circumstances, all of a copyrighted work, even where the copyright holder has not given permission or objects.
How does fair use fit with copyright law?
Copyright law embodies a bargain. It gives copyright holders a set of exclusive rights for a limited time period as an incentive to create works that ultimately enrich society as a whole. In exchange for this limited monopoly, creators enrich society by, hopefully, contributing to the growth of science, education and the arts.
However, copyright law does not give copyright holders complete control of their works. Copyrighted works move into "the public domain" and are available for unlimited use by the public when the copyright term expires. But even before works enter the public domain, the public is free to make "fair uses" of copyrighted works.
What has been recognized as fair use?
Many types of uses have been found to be fair. Here's a small sample:
For more information, check out the FAQ at the Electronic Frontier Foundation