As I want to keep this guide brief and to the point, I won't be going into much detail about the history of Creative Commons (CC) etc. For more information check out the Creative Commons website which I will post a link to in the comments.
'Creative Commons helps you legally share your knowledge and creativity to build a more equitable, accessible, and innovative world' (CreativeCommons.org)
Basically this means that creative commons allow the internet to be more open to everyone. If everyone on the internet completely owned their work, not letting it be shared or built upon, the world would be a lot more limited and there would be a lot more suing.
The best examples of this is Wikipedia and YouTube. People all coming together to work and possibly bring about change. Change such as scientific developments when scientists share results or even political change.
And what about 50 Shades of Grey? Wasn't that a fanfiction of Twilight?
Creative commons allow work to be built on. So it can be used (given a new purpose), remixed (changed/adapted) and redistributed (shared again).
I will be discussing the details of CC licences in the next few chapters.