Hookahs are used mostly for flavored tobacco these days, although you can use them for other stuff. (However, I wouldn't recommend it since hookahs usually hold a lot of whatever you're smoking, and are meant to be used by multiple people at once.)

You won't get in trouble for buying a hookah, pipe, or otherwise as long as you're old enough to do so.

Yeah, they also call them E-Cigs (Electronic Cigarettes) but I think that's kind of a misnomer because you can get a lot of juice mixtures which contain no tobacco or nicotine whatsoever.