Personal Question

I've decided to talk about how I think cable works mostly because I've never thought about it before, and don't really have a clue.
What I think is most interesting is that my house here in Gainesville gets cable AND highspeed internet through the same cable jack. So this cable, connected to our telephone pole, which is then connected to COX someplace, is sending the television information (all digitized, it has to be) to any TV thats hooked up to it. Can't be a very complicated system, because you plug that cable in and there are all the channels, you don't need to reboot the tv.
Some how that same information, when connected to a modem, can give us high-speed internet. Now, either both systems are flying through the same cable, which I don't understand, or the same information is used for both, which confuses me more.

ALSO- they're able to control what package of cable/internet we've purchased and manage what information they dole out to us and every other house on the block.
I can comprehend how they manage this information, just not how they control it through this simple coaxial cable. But then- I'm not that savvy.