Where are the .desktop launcher files in Pop OS?

I needed a reminder of where to look, and the first search result was in a reddit post on r/pop_os with a similar title. Since that sub is currently locked, I found my answer elsewhere. I decided it would be useful to post the info here too. I'll write my answer below, and someone can write a better one if they have it.

(p.s. Thanks for keeping the reddit sub private; I think it's the right decision since the major reasons for the blackout have not changed.)