So…is it really unlimited? What about throttling?

It really is unlimited, yep.  So no extra charges for using a certain amount of data.  And no throttling either.  So it doesn’t automatically slow down after you hit a certain threshold.  That said, remember that it works kind of like a pipe and sometimes the pipe gets full.  When that happens, T Mobile has to figure out how to get everyone who wants in the pipe in it in an orderly way.  Just like a highway or a crowded restaurant, there are ways that they manage the “over demand” in a logical way.  So, there may be times when the network slows down or you may have to wait your turn (and it slows down).  If you want to read all about it, you can go to https://www.t-mobile.com/responsibility/consumer-info/policies/internet-service.