We have Lemmy.world, Lemmy.ml, beehaw.org, I think even yiffit.net. If I log in using wefwef it asks me where I want to login. And when I make a new account using another instance, it says ”… Lemmy is federated, so you can interact with everything on lemmy.ml even if you’re registered on a different instance.“ So if I’m registered on lemmy.world, how can I interact with lemmy.ml?
I can (could) post to reddit with Boost, my friend uses Apolo, this other guy uses RIF. To the layman what’s the difference between my instance, your instance, wefwef, jerboa, etc. The general public don’t know about email servers any more than Lemmy instances.