How are films in theaters delivered?

So obviously in the days of analog I’d imagine depending on how many theaters a movie was showing in a few reels of film would come in via mail and that would be that. But in today’s digital world I imagine it’s a little different. I assume that the files for movies in theaters are of a higher quality and resolution than what we watch at home (especially over 1080p). So I’m assuming movies don’t get delivered on a blu ray disk. Are they downloaded now? Basically any light anyone can shed on that would be helpful. I’ve always wondered about how different theater versions of movies are compared to home releases. TIA.