Adding to what the other guy said, you can think of Lemmy as a collection of servers. Right now you're on lemmy.ml, but some people are on https://beehaw.org/ for example. Beehaw is also Lemmy, but it's a different server with different users and communities.
Here's what makes the Fediverse cool though. You don't need to go there to interact with them. You can stay on lemmy.ml and access and comment on Beehaw. When you're on the home page it defaults to "Local", but if you click on "All" you can see posts from different servers. Same thing when you click on "Communities" at the top. It lets you browse communities on different servers by clicking "All".
Let's say you wanted to browse the gaming community on Beehaw. You can write "gaming" in the search field and find gaming@beehaw.org, or you can just type it into your search bar as https://lemmy.ml/c/gaming@beehaw.org
Now you can browse, comment, vote, and interact with that community. I posted this comment from https://kbin.social/ , which is NOT Lemmy, but since the Fediverse is connected we can basically interact with each other from different websites.
A detail that is useful to keep in mind, as it can explain some edge cases, but which isn't critical to actual day-to-day usage, is that whenever you're viewing a community hosted on another server, you're not viewing the content on that server. Instead, you're viewing a mirror of it hosted on your local server.
This means there may be comments or posts viewable on the community's host server that you're not seeing yet, because they haven't been passed along to the instance you're using yet. The remote community needs to actively forward new posts and replies to instances that are following it.
This is also why if you follow a remote community from a new instance -- that is, you trigger the mirroring -- you won't necessarily get the whole backlog of posts from the community. Just like how if you subscribe to a magazine, you only get future print editions (they don't send you their entire back catalogue), when an instance subscribes to a remote community, it only receives future content.
Interesting, do you think this approach will limit how big Lemmy can get? For example, if a server wanted to subscribe to ten communities that are the size of large subreddits, how much data would that be? How much would it cost to maintain a server that could handle that?
Reddit is like going to Chucky Cheese for your birthday. It’s fun, but it feels a little forced and ultimately the point is for Chucky Cheese to sell you terrible pizza.
Lemmy is like being left alone during summer vacation with nothing to do and one of your friends hands out walkie-talkies and you all hang around the neighborhood and make a game of stalking the mail carrier and there’s absolutely no point but afterwards you get real pizza at Salvatore’s.
It's Reddit but federated. A federated service is one that works like e-mail, i.e. there are multiple providers/servers/instances but all of them are connected so it doesn't matter which one you choose. Additionally, Lemmy is federated to other services (e.g. Mastodon), forming what's known as the Fediverse.
So one thing I don't understand is, how do all the federated servers find each other? Is there one server that maintains the registrations to all other servers and each server can pull from there? What happens if that central server decides to delete another server from it's list, doesn't that put authority back into one server/persons hands? Or does each server maintain their own list of federated servers and if so you never know if you're fully connected / how much time would that take each server owner?
No, there's no central server. To my knowledge, servers federate either manually or by their users manually exploring other servers. But most servers at the moment are already federated with each other.
What's the difference between the multiple lemmy instances and something else also ActivityPub based like kbin? Is lemmy.ml vs lemmy.world the same as comparing lemmy.world with kbin.social? I have accounts with both Lemmy and Kbin and confused a bit by what I'm seeing, and also Threads vs Magazines vs Microblogs haha. So much to learn about the fediverse!
Well, the software they run is different. The frontend looks different, etc. Lemmy can connect with kbin, as well as Mastodon, so it's just one big network at the end of the day.
The best way i can describe it is with Runescape. Users can access different worlds(or "instances") and every world runs the game. However unlike runescape every world is independently run and which world you form your account on determines which other worlds you can see and interact with.
There was a good discussion of this topic in another post recently. Here's the comment I posted trying to cover some of the fundamentals: https://lemmy.world/comment/20357. But the whole post is pretty helpful.