I am new and trying to understand how Lemmy works. I am posting this from my lemmy.world account, on a lemmy.ml community. It seems like you can read, post, subscribe to whatever community outside of the instance you’re registered with. So… Why register on lemmy.world vs lemmy.ml or any other instance, if all communities are accessible to everyone?
Load distribution. Different Lemmy instances are run by different volunteers who can only put so much money into them. So if lots of volunteers put up their own instances, then ideally each instance could have a few users signed up and thanks to federation, they’ll all be interconnected.