Do Jews believe in hell? I genuinely don't know.
Not really, at least not in its conventional/Christian sense. The idea of olam haba (a "world to come") is quite universal in Judaism, both applied to afterlife and messianic times, but what olam haba (and Gehennom) essentially are is not exactly set in stone. The entire area of afterlife is seldom discussed and does not get much attention in Judaism in general, though there are, in fact, myriad different visions on it. To give you an impression,
this is one of them, explained quite simplistically, but it is very much influenced by Chabad's hasidic outlook and by no means universal to Judaism (to the point that I probably know rabbis who think almost everything in that article is bull[inks]).
Poll
