do you not go to the movies in the US? Fandango is one of the only ways you can prepurchase tickets - their kiosks are at every theater I've been to over the last ~10 years.
I think many purchase online directly through the theater. I used Fandango until I started using AMC's app directly, since most of the theaters I'd want to go are AMCs.
Canadian here, Fandango's one of those names that you hear and it rings a bell, but chances are you haven't really interacted with them and don't know much about them beyond them being in the ticket sale/resale space broadly.
Well they were at one point. I'm a bit of a dinosaur, so I was alive before either of these existed. I'm left wondering what people do now. Have an app for each theater perhaps?
Edit: I don't believe sonicxxg deserves any down-votes. After all, everyone doesn't know everything. Obligatory xkcd: https://xkcd.com/1053/
The local paper, especially if you had a free weekly "alternative" paper in your locality, was where you'd pretty much find anything. The great thing, looking back on it, was that it wasn't "customized for your taste" and you could learn a lot by looking at the listings. Unfortunately, the internet wasn't as good at giving information about stuff until about 1993 so you'd have to ask friends if they knew anything about that band with the cool name. The advertising was relevant and nonintrusive. Instead of the whole paper being covered in ads for the new Avengers movie like IMDB, there'd be ads for several of the new releases, some new record releases, bands coming into town, art shows, etc.
I think the confused person must live in Europe. I hadn't heard of any of these services and I've lived in UK and Czech Rep ... however over here we're all pretty used to the "ohhh this must be an American thing" feeling so I'm not sure why they're acting all surprised