Creative Commons encourages copyright holders to share the information they have copyrighted more freely. When using Creative Commons, a copyright holder can make modifications to the traditional copyright assumed as part of the Copyright Act. "With a Creative Commons license, you keep your copyright but allow people to copy and distribute your work provided they give you credit — and only on the conditions you specify..."1 Once registered with Creative Commons, the copyright holder displays symbols showing these modifications.
An excellent video on their website explains the Creative Commons concept.
1. Creative Commons, "License Your Work," Creative Commons, http://creativecommons.org/choose/, January 9, 2010.