So, there's three different levels of organization on the fediverse: the software, the instance, and the community / magazine. For the moment, I'm just going to focus on how kbin works-- we'll bring lemmy back into the conversation in a second.

So "kbin" refers to the actual software that makes everything work. It's the code that displays your posts, shows them to other users, processes upvotes and downvotes, all the other nice bells and whistles that make the site work.

But software can't exist on its own, it needs to be run on a server. On a centralized social media site like reddit, the same company that writes the reddit software also hosts all the reddit servers. But there's no company backing kbin, as far as I'm aware it's literally just one Polish-German dude who, unless he's secretly been a billionaire this whole time, can't afford to run all the servers needed to host all the traffic kbin's recieving.

Instead, many different groups have volunteered to run servers. These groups are the instances. Kbin has several different instances/servers-- the largest is kbin.social, but there's also fedia.io, readit.buzz, and karab.in, among many, many others.

Finally, each instance can host as many or as few magazines (subreddits) as it wants to host. The cool thing about the fediverse is even though each instance is hosted by completely different, unaffiliated people, if you make an account on one instance you can interact with magazines hosted on any instance you want.

But wait, what about lemmy? This is the part where the Fediverse is pure, unadulterated magic.

Because lemmy? It's a totally different piece of software than kbin!

That's right: lemmy is written by a completely different team of devs, and works in completely different ways to kbin on a technical level. Lemmy instances (servers) only run lemmy software. And lemmy communities (subreddits) are hosted by lemmy instances using the lemmy software.

And yet, through the pure magic that is the fediverse, people using kbin-- a completely different piece of software-- can still browse lemmy communities, vote and comment on lemmy posts, subscribe to lemmy communities hosted on lemmy instances running lemmy software. And lemmy users can interact with kbin magazines hosted on kbin instances running kbin software.

Here's the part that really blows my mind. This interoperability isn't limited to the two reddit analogues. You can interact with any fediverse_ software from any fediverse account, no matter what instance it's hosted on or the software that instance is running. You know Mastadon, the fediverse twitter analogue? You can actually interact with Mastodon posts from kbin or lemmy! And vice versa-- Mastodon users can interact with kbin / lemmy posts. The only limit is the user interface of whichever software you're using. (Kbin makes it a little easier to interact with Mastodon, which is one of the reasons I prefer it to lemmy, but it's possible from both.)