Creative Commons provides legal tools to give everyone, from individual creators to large companies and institutions, a simple, standardised way to grant copyright permissions to their creative work. The combination of these tools and their users creates a pool of content that can be copied, distributed, edited, remixed, and built upon, all within the boundaries of copyright law.
There are 6 Creative Commons licenses and a public domain mark. Together they allow for more options than only all rights reserved. The public domain mark, CC0, is a legal tool that makes it possible to waive all copyright and related rights in a given work. Everyone is free to use the work under any circumstances.
For more information, visit the license page on the Creative Commons website.