Creative Commons (CC) was created to allow creators more control over how and when they allow their work to be used. They provide tools that "give every person and organization in the world a free, simple, and standardized way to grant copyright permissions for creative and academic works; ensure proper attribution; and allow others to copy, distribute, and make use of those works."
CC flips the traditional copyright model, in which all rights are reserved except those expressly granted. Instead, under CC all rights are granted except those expressly reserved. The creator still retains legal ownership of the work; however, unlike traditionally copyrighted materials, all CC materials may legally be redistributed to anyone, at any time, indefinitely.
In addition, most CC materials can be revised and remixed before being redistributed. The exact permissions allowed for a particular work depend upon what CC license is applied to it.