Other forms: public domains
When something's in the public domain, it's available for anyone to use. Since the copyright for "Moby Dick" has expired, it's in the public domain. Have at it!
Ideas, facts, and government documents are just some of the things that are in the public domain. When something (like a book or a song) is under copyright, it's not in the public domain. People who want to use these materials have to pay a fee to copy parts of the book or record a new version of the song. Eventually a copyright expires, which puts the work into the public domain. A good example of this is the song "Happy Birthday," which is now in the public domain — you can officially sing it without paying a fee.