You know how when you were a kid there were the ‘cool’ but obnoxious kids, that’s Reddit. What we have here is the quiet cute kid playing a GameBoy in the corner of the room, that’s Lemmy.

maybe this is a good start to read https://tech.michaelaltfield.net/2023/06/11/lemmy-migration-find-subreddits-communities/

and then for more details https://join-lemmy.org/docs/en/introduction.html

What is it you don’t understand?