It's mostly just a reddit clone, but it's broken up into different servers with different URLs. Nominally you can interact with all the other servers (your account might be on lemmy.ml, and the most popular r/privacy might be on lemmy.world, but that does not stop you from interacting and posting on that subreddit).

But ultimately a bunch of the servers got into fights over political differences and a lot of them blocked each other. So everything got fragmented and it became hard to keep track of which communities could interact with which.

In my experience there was also a weird number of "CCP did nothing wrong" type people over there. Things seemed to devolve very quickly into "Western countries bad," moreso than reddit.

Sigh. Especially frustrating considering his comment down the thread reveals the "annoying defederation drama" he talked about was relating to Exploding Heads.