A lot of us are still learning, but I think I'm figuring it out here. I was/am on kbin too, but they aren't federated with anyone so it's just a reddit clone currently, and it was hard to understand without context.

If you go to magazines and search, you can see some with normal names and some with @ names. The normal named ones are here in Fedia, the @ names are a different instance (Lemmy, Beehaw, kbin when it federated). You can subscribe to communities there and see their content, interact with the users, etc like you would normally. You won't even be able to really tell the difference.

The part where it differs from reddit is that you will have multiple of the same sub, as each instance grows. Ideally, you would start with an instance you agree with 100%, but that's not realistic. So as you navogaye the Fediverse (hate that term), you'll see where you fit in best with instance rules and ideology. Assuming everything is still fairly similar, you would be able to federate with the same instances and still see the same content, but from the instance you choose.