Kbin is also like Mastadon. It’s basically the same thing as lemmy, just with a slightly different user interface. (I personally like it better, which is why I’m here, lol.)

The main kbin instance, kbin.social, is hosted by a guy called @Ernest, who’s also the main (only?) dev who created kbin. But there are other kbin instances hosted by totally unaffiliated people, too.

I’m no expert but I can do my best. Kbin was created by @ernest, and is actually a very young platform compared to even Lemmy. It let’s you post threads, similar to Reddit or Lemmy. Like Lemmy, it also uses something called ActivityPub, which means that Kbin users can see and comment on Lemmy threads and vice versa as long as the instances (ex. Lemmy.world, kbin.social) are “federated” meaning that they are talking to each other.

One of the big differences is that Kbin supports microblogging as well, similar to a Mastodon or Twitter post. Because of this, you can see and interact with content on Mastodon from Kbin much more easily, which also uses ActivityPub. Lemmy can also technically interact with Mastodon but it is not as seamless as threads don’t display that well on a microblog and vice versa.

There’s some more technical and cultural differences as well but I think that’s the biggest difference in function.