Creative Commons is a nonprofit organization that enables the sharing and use of creativity and knowledge through free legal tools. Creative Commons licenses are not an alternative to copyright. They work alongside copyright and enable you to modify your copyright terms to best suit your needs.
The licenses below and their descriptions come from the About the Licenses page of Creative Commons.
Copyright is a form of protection grounded in the U.S. Constitution and granted by law for original works of authorship fixed in a tangible medium of expression. Copyright covers both published and unpublished works.
Article 1, Section 8 of the U.S. Constitution states:
"The Congress shall have power...To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries..."