Ten years ago Creative Commons (abbreviated "CC") was born. Lawrence Lessig, political activist and director of Harvard's Safra Center for Ethics founded Creative Commons based on an assumption that the age-old copyright law was outdated and needed revision. In our new media and information landscape people are not simply passive consumer, but are also creators of media on a large scale.
Source: Lessig, Lawrence. "A Message from Larry Lessig." 12 Jan. 2012. E-mail; creativecommons.org
In this case, there is no better place to go for information than the source.
Source: Creative Commons
Watch this brief video from Creative Commons to get a basic understanding of what Creative Commons is and why it exists.
Source: Creative Commons
Watch this video, also from Creative Commons, and gain a further understanding of how Creative Commons licensing works, who might use it and why.
Source: Creative Commons
If you'd like to look a little bit further into Creative Commons and how it has been used, spend some time exploring the case studies archived on the CC website. There are tons of examples of CC licensing in action and the difference it has made. There are examples from music, film, education, art and more.