Who decides who can become an ISP? Does it have something to do with the W3C? Does it have something to do with which companies paid for the infrastructure of cables and crap? If that is the case how did AOL become a provider?

On a similar note how do companies sell domain names? Who gave them domain names to sell? (I understand how squatters work though)

So many questions. I've have now shown my complete ignorance if I haven't already I'm sure. Thanks for any enlightenment.