But that is basically it from the users standpoint. Under the hood it’s as if all of these separate forums can talk to each other and if you post on one forum it gets copied to all of the other ones.
So if you want or subscribe to something, just go to the subscribe tab and you will see all of the lemmy compatible sites even if it’s not the site you originally signed up at.
In 5th grade they defined every kid that can speak another language as ESL (English as a second language) even if you spoke English perfectly. Then they put all of the ESL kids in a different class on the opposite side of the school. The result was that the school became de facto racially segregated with all Asian and Latino kids on one side and all white kids on the other. It’s not like it served a purpose anyway since none of the teachers could speak anything other than English.