Free content is any kind of functional work, artwork, or other creative content having no significant legal restriction relative to people’s freedom to use, redistribute, and produce modified versions of and works derived from the content.

Free content encompasses all works in the public domain and also those copyrighted works whose licenses honor and uphold the freedoms mentioned above. Because the law by default grants copyright holders monopolistic control over their creations, copyrighted content must be explicitly declared free, usually by the referencing or inclusion of licensing statements from within the work. (source: wikipedia )

The most familiar web site with free content is the free encyclopedia Wikipedia and its sister sites but also other pages offer free content released under licenses guaranteeing the freedoms mentioned above.