Creative Commons is a free licensing system that allows the author of a work to specify legal permissions for how the work may be used others, while retaining full copyright to it themselves. Creative Commons licenses are not an alternative to copyright. They sit on the shoulders of copyright law, and allow authors to easily modify copyright terms to encourage collaboration and sharing.
The 
symbol indicates that a work is held under Creative Commons License. CC licenses include four rights that allow authors to add or subtract specific permissions. These rights can be combined into six different Creative Commons Licenses as illustrated below:
"How to License Poster" by Creative Commons and adopted from Community College of Allegheny County (CCAC) website.
The concept of open education recognizes that knowledge is built upon what came before it. Creative Commons Licenses encourage collaboration and sharing. They ensure that content is freely available for the 5Rs of Open Education: revise, reuse, remix, redistribute and retain, as described by David Wiley. These permissions allow materials to be tailored and adapted to suit different needs, while still recognizing the original copyright. Creative Commons Licenses let educators know which items are freely available and how to give the creator credit. Consider sharing your own work with others by publishing under a Creative Commons license.
Adopted from Community College of Allegheny County (CCAC)