Basically all the content is mirrored on each instance. So you can create an account on any instance, and join communities hosted on any other instance.

The only exception is it seems like some instances are blocking each other

I’m one of the new Lemmy users, fleeing from the sinking ship that is Reddit. Hi everyone!

Thank you it all makes sense now

The interface is nice and friendly, but the way the fediverse and the different instances works is kind of confusing. Still not sure what that’s all about