There are many good resources about Creative Commons on the web. I have used a film from Creative Commons New Zealand whenever someone have asked me to explain CC Licences. The short video is a really good introduction with great drawings and examples.
To make it even more suitable to be used as part of my standard OER talk I have re-mixed it and made a version that is just over 3 minutes.
In this short version I have stripped it down and focus only on the core elements and the explanation of these.