Honestly just don't think about it too much. Just use it like you used reddit. You're on lemmy.world, other people will have initiated the federating link for most communities anyway
Welcome! It's a bit of an adjustment but now that there is no other option but to move, we all can do our parts to make this be the active platform we all need our addictions need a fix of
Welcome! I’m only a few days into my journey to figure this out, and one thing I can say is that the community here is very helpful and friendly - most of us are in the same boat and all just trying to learn.
Keep an eye out for Memmy (iOS app, currently in beta/TestFlight). I’ve been using it for a week and, as an Apollo user, it feels comfortably familiar.