Public Domain
The term public domain has slightly different meanings depending on the context. In copyright, the term is used when the copyright in a work has expired and the work can be freely reproduced, performed or used without needing permission from the copyright owner. The more common usage of the term - refers to information available on the Internet and means that it is freely available for users to access. However public domain material on the Internet may still be subject to copyright and may be freely reproduced, downloaded or performed etc. Copyright law applies to information on the Internet in the same way as hard copy information.
To make matters more confusing some material on the Internet is considered public domain because it is freely available on the Internet and because copyright has expired. An example of this is Project Gutenberg.
See also Duration of Copyright and Internet & Web Publishing.