Just joined Lemmy today. From what I understand, there are different Lemmy instances that host different communities. I supposed that to interact in a community hosted in a certain instance, I would need to create an account for that instance. Ended up creating 10 different accounts.
Instances talk to all the other instances through federation. You only need one account on one instance- from there you can then go to communities on other instances by linking !community@instance.tld (e.g !memes@sopuli.xyz) and/or looking them up in the Communities tab and interact with those communities from your home instance.
Except a lot of times some comments don't show up depending on which instance or platform you're visiting from. The only one that's showing all comments for me in my (very limited) testing is kbin.social but there's no mobile app for that (yet). So on lemmy I've been jumping around between some accounts to try and see which one will show me most of the content