I still don't get it, personally. I just joined the one I'm on because it was the first one I saw
I have no real understanding of what's going on or how it's didn't from reddit other than one person can't power trip on it.
Think of it like different email providers. There are a few big ones, and some people host their own, but they can all (usually) communicate with each other.
Alright, that tracks. But then how/ why do I see stuff from the other instances (I think that's the right word)? Are they all like different subreddits?
That would be the different email providers in the analogy. Each instance has its own set of communities (subreddits). But if the instances are federated with yours, then you can see the communities of those other instances