1.The copyright law is the law of the United States that protects the works of authors, artists, composers, and others from being used without permission. Fair use allows you to use a limited amount of copyrighted material as long as it is for educational reasons.
2.The works protected by copyright are literary works, musical works including any accompanying words, dramatic works including any accompanying music, pantomimes and choreographic works, pictorial, graphic, and sculptural works, motion pictures and other audiovisual works, sound recordordings and architectural works. The works not protected by copyright are ideas, procedures, methods, systems, processes, concepts, principles, discoveries, or devices,titles, names, short phrases, and slogans, and mere listings of ingredients or contents, works that are not fixed in a tangible form of expression, such as an improvised speech or performance that is not written down or otherwise recorded, works consisting entirely of information that is commonly available and contains no originality, and works by the u.s government.
3.Public domain is works that are not copyrighted.You can use it without permision as long as you give them credit of were you found your work.
4.You can use up to 10% in your work or in your game.
I got my information from http://www.copyrightkids.org/ and http://www.cyberbee.com/cb_copyright.swf.
