This actually first started years before I was born, and even after I was born, I'm sure it was many years before it aired on a channel I got. There've been different hosts over the years, but Alex Trebek began hosting long before I ever got to see the show (which was probably in the mid-to-late 80s). And he's still the host. Anyway, I'm not sure what to say. Contestants have to answer various questions in various categories, to win various amounts of money. And whoever has the most money at the end of the episode gets to come back to compete on the next episode. I don't think there's any limit to how long a contestant can keep returning, as long as they keep winning. But usually their streak will end before too long. Um... anyway, the theme music is kind of iconic, and the show itself has become a prominent part of pop culture, being parodied or utilized as a plot point in episodes of any number of sitcoms or comedy shows (notably Saturday Night Live. Jeopardy can be fun to watch, if I've got nothing better to do, but even then it usually wouldn't occur to me. Even if someone else is watching it, I wouldn't be likely to wander into the room and watch it, myself. But... on rare occasions, I guess I still tune in for at least a few minutes.
Oh yeah... and of course it must be noted that the "questions" are phrased in the form of answers, and contestants are required to phrase their answers in the form of questions. Which is stupid and pointless on the surface, but even stupider when you really think about the fact that if someone actually asked the specific questions contestants are meant to ask, the answer would rarely be the one given by the show. It just doesn't make sense. But it's something you just have to get over, if you're gonna watch the show. Some people can't. (I know my dad complains about the format often enough, though I'd figured this out long before I ever heard him do so.) Although I must say, the format was amusingly spoofed by one aspect of Win Ben Stein's Money.
Oh yes, and there was a commercial I remember fondly from the late 80s, because of how redonk it was.