Are communities with the same name, but different instances linked at all? e.g., Does /c/asklemmy@lemmy.ml and /c/asklemmy@lemmy.world have any relation?

I understand that a user on any instance can subscribe to any community in the fediverse, but I have been a bit confused when searching for communities to join. Sometimes there are communities on different instances, with the exact same name.

• Do these communities talk to each other at all, or are they completely separate, with a different host, posts, mods, subscribers etc.

• Should I just join the largest (and presumably, most active) one?

• Is there anything in place to discourage communities of same name, but different instances, from “competing”?