You might be wondering why Creative Commons was created. The following quote from Professor Lawrence Lessing is a good summary of the reasoning behind it:
“The idea motivating the Creative Commons is the reality that copyright law by default gives copyright owners what’s referred to by the slogan “All Rights Reserved.” And for most people on the Internet, that’s more protection than they actually want. But there’s no easy way to signal that I don’t need all this protection and I’m happy to give up some rights. So what we [the Creative Commons organization] did is build a tool, a technology, that makes it easy for authors and artists to signal the kinds of rights they are happy to give away, while signalling the rights that they want actually to keep. So it facilitates sharing and building and remixing on top of content where the authors opt in to this more balanced and rational copyright system that supports the idea of remix or participatory culture.”
Optional: read An Overview of the Creative Commons, which has information about its purpose and also about all the licenses and how to use them.