I see tons on the secondary market, but i was wondering what exactly happens after a movie wraps.
It varies widely. Sets of interiors are always struck (torn down) as they can’t be stored or moved. Everything else is generally the property (where the word ‘prop’ comes from) of the studio and goes back into storage. Highly specific things will get special treatment, i.e. stored for sequels, put on exhibit, or if the prop cost a lot to make and the movie flops sold for scrap etc. Back in the day reusing props from film to film was just SOP, but these days because of internet fanboys it’s a little embarrassing for a big movie’s more obvious props to be spotted in another film. It’s still much more common in television. Here’s a neat article about prop reuse in all the Star Trek series.
Because prop reuse was absolutely standard procedure in old Hollywood science fiction films (because of their expense) Stanley Kubrick made sure that every prop & model from *2001 *was destroyed.