Public domain
Public domain is a term used to describe things that are free for anyone to use. This could be a song, a book, a photo, a video, or any other piece of work. It means that anyone can use the work without having to get permission or pay a fee. Because of the public domain, many people are able to freely enjoy books, music, and other works that would otherwise be out of reach.
Related topics others have asked about:
Center for the Study of the Public Domain,
Copyfraud,
Copyleft,
Copyright Term Extension Act,
Copyright status of works by the federal government of the United States,
Eldred v. Ashcroft,
Fair dealing,
Free-culture movement,
Free software,
Freedom of panorama,
Limitations and exceptions to copyright,
Millar v Taylor