Creative Commons is an organization devoted to helping creators (copyright holders) share their information freely and openly on the web.
Creative Commons Licensing is a simple direct method of communicating, as the copyright holder of a work, what others have permission or are restricted from doing with your work.
"Creative Commons licenses free of charge to the public. These licenses allow creators to communicate which rights they reserve, and which rights they waive for the benefit of recipients or other creators. An easy-to-understand one-page explanation of rights, with associated visual symbols, explains the specifics of each Creative Commons license. Creative Commons licenses do not replace copyright, but are based upon it. They replace individual negotiations for specific rights between copyright owner (licensor) and licensee, which are necessary under an "all rights reserved" copyright management, with a "some rights reserved" management employing standardized licenses for re-use cases where no commercial compensation is sought by the copyright owner." From Wikipedia
It should be emphasized that it work with Copyright not as a substitute. Items with Creative Commons licenses are subject to fair use and educational exceptions to the copyright laws as is any copyrighted work.
The links below will provide more information on the various creative commons license as well as places to obtain images, music, and other objects that have these license, so users can easily know what restrictions or options are available for users.