There are six types of Creative Commons licenses:
Attribution – ShareAlike;
Attribution – No Derivatives;
Attribution – NonCommercial;
Attribution – NonCommercial – ShareAlike; and
Attribution – NonCommercial – No Derivatives.
The Creative Commons form licenses are particularly useful for people who want to share their work as broadly as possible on the Internet. Rights granted are broad and are intended to facilitate sharing as well as mashups and derivative works. Although some creators find Creative Commons licenses useful for expanding access to their works, this may not be the appropriate approach to take with works you think may have a commercial value you may be interested in exploiting now or in the future.
As long as the use of the work is consistent with the license, a Creative Commons licenses attaches to the work and authorizes everyone who comes in contact with the work to use it according to the terms of the license. This means that if Charlie has a copy of your Creative Commons-licensed work, Charlie can give a copy to Susan and Susan will be authorized to use the work consistent with the Creative Commons license.
Finally, because Creative Commons is a non-profit organization, and not a licensing entity, tracking of uses to ensure consistency with the license grant and enforcement against any breaches is up to the copyright owner electing to use the Creative Commons license. This is in contrast with some other licensing entities and collecting societies that license specific uses of the work of their members for particular terms and are responsible for monitoring and ensuring compliance with license terms, and collecting and distributing royalty payments to the authors.