Open Source, Mix Culture, and Peer Production

What does "open source" really mean? How does Wikipedia work? What is a creative commons license? What kind of attribution do you need to give for various kinds of borrowings? How can you make it clear to people that you want them to use your stuff? How do libraries/communities like Autodesk and Thingiverse work? Why would you want to open source YOUR stuff? What do you need to do to do that?