I test drove a Model S a few weeks ago, and asked a similar question. (However, an actual owner might know first hand -- I'm just a Model 3 reservation holder.)
They told me that the car connects to the internet for maps, updates, etc. This connection is built into the car, and we don't have to do anything to maintain it. There's no account to set up, or bill to pay. It's just part of the car. However, we can not use that connection for our personal devices (i.e., the kids can't stream movies off of that connection). It's just for the car to talk to Tesla.
I hope this helps.