How exactly does waitlist work?

I didn’t know where to post this, sorry Hello, I really just want an explanation, because I’m a little confused. I’ve been wailisted at Colorado College and University of Virginia. I know that chances of being admitted through waitlist is slim to zero, but what exactly happens? If we have chosen a different college on May 1st, are we no longer on the waitlist? That would kind of suck if we didn’t reply to a college we were admitted to and decided to stay on waitlist and end up not getting admitted in the end. Someone please explain to me, thanks lol. UVA was one of my top choices but I’e already gotten into a few colleges I want to go so I’m not really putting all my faith on the waitlist. Thanks to whoever replies!

You opt into the waitlist at either or both schools. You SIR (enroll) before May 1 at one of your accepted schools. You remain on the waitlist until you hear either way. If you are accepted off the waitlist, you are given a few days to accept or decline. You then withdraw your enrollment from your first school that you SIR’d and enroll in the waitlisted school. You will however lose your enrollment deposit from the first school and sometimes part of any housing deposit you have made.