Lemmy isn’t a single website like reddit.com is. It’s rather a collection of decentralised servers (“instances”) offering the same service (one very similar to reddit). It’s often compared to e-mail - just as Gmail users can talk to Outlook users, lemmy.world users can post and comment on lemmy.ml from their home instance.

What this does is it removes the centralised aspects of Reddit - if a community has powertripping mods one can make an alternate community (like on Reddit). But this goes a step above - powertripping server admins can be reigned in by simply switching instances.