What does "public domain" mean?

As defined by Wikipedia, “the public domain is a range of
abstract materials—commonly referred to as intellectual property—which are not owned or controlled by anyone. The term indicates that these materials are therefore "public property", and available for anyone to use for any purpose.” To learn more about content in the "public domain", please refer to the following resources:

http://www.copyright.gov/fls/fl102.html
http://fairuse.stanford.edu/Copyright_and_Fair_Use_Overview/chapter9/
http://www.copyrightwebsite.com/Info/Law/FairUse.aspx