Creative Commons is a non-profit organization that is dedicated to empowering individuals to legally use and re-use creative works through the development and availability of legal tools to supplement copyright globally,.
Creative Commons licensing works with copyright and international property rights to provide legally binding tools for transferring some of the rights for a work from the rights holder to the user.
Materials that are licensed in this way encourage the re-use and re-mixing of works and provide greater public access.
Copyright is a protection offered by law to authors of original works affixed in a tangible medium. While it is no longer necessary to register your works for copyright, this symbol is still a common representation of copyright. 
Copyright assumes that "All Rights are Reserved" -- reserved to the author or rights holder.
Those rights include the right to:
Creative Commons and other licenses assume "Some Rights are Reserved."
Licensing a work allows you to maintain your copyright while allowing others to perform activities with your work that are generally reserved for the author or copyright holder such as making physical copies, adapting your work to other situations, and distributing the work.
There are several open licensing organizations. Creative Commons is one of the most widely used. The ideal license will offer a human readable and machine readable. A legal instrument supports these notices.
As you can see below software developers were among the first to develop open licensing.