Copyright is a personal property that protects the original author/creators work. In order to use someone's work for any reason you have to ask and also receive permission. Some examples of Copyright include, Books, Articles, Music, Websites, etc.
Fair use: The Fair Use policy Does Not Allow Copyrighted work to be Copyrighted.
It also has rules and regulations that are also set in place for us to use other peoples ideas without getting into trouble.