Lemmy is one of those things you must use for a while to fully get. It all sounds a bit complicated at first, but the federation works well when it does work, and you really can have one account here (or anywhere in the Lemmy federation) and access the rest of Lemmy.
From the ground up, Lemmy is built on the idea of instances. If you're reading this, you're currently visiting NormalCity, the instance of Lemmy I personally host. Lemmy would be pretty difficult to use if you had to sign up for a different account on each instance you wanted to join, as a lot of great communities are spread across dozens of instances. That's where federation comes into play; it's essentially the magic word for "linking together," and it's how Lemmy can act like one site, even though there's no central server controlling things. In reality, Lemmy uses the ActivityPub protocol, which allows servers to "talk" with one another and exchange user interactions and information in real-time. So, what does that mean for you? It means that you can sign up for an account on, say, NormalCity, and still talk with, subscribe to, and be a part of communities on Beehaw. You can access and subscribe to every community, talk with every user, and have a front page like you might be used to on Reddit. As long as you find a place you feel comfortable signing up for an account and the server you're connected to is well-federated (like NormalCity), you're just as much a part of Lemmy as anyone else.
Now, I might add that choosing where to sign up for an account is more important than you think. For example, as an admin on this server, I can act like one of the Reddit fat cats; I can delete your account, I can control local communities, and I can even block you from seeing certain content out in the fediverse. Heck, if I wanted to, I could even block (defederate) a ton of instances willy-nilly. Obviously, this is a ton of power to have, so it's important to find a place that actually cares about the user experience. Oh, and problematic Lemmy instances are often defederated from most of the larger instances, and politically divisive instances are often the target.
This instance, NormalCity, is focused on providing an excellent experience disproportionate to our small size. We're open to federation and will only remove federated content in limited circumstances. We're open to registration (and are currently accepting applications), which means you can sign up for an account at your leisure. We also have a basic set of instance-wide rules akin to Reddit's Code of Conduct. You are free to create communities here, so long as they are topical to NormalCity's focus on creativity and technology (and follow the aforementioned instance-wide rules). NormalCity wants to deliver a true vanilla user-first Lemmy experience while providing local communities that are apolitical and focused on topics that relate to creativity and technology.
Now, you might be catching on to the idea that communities and instances (servers) aren't the same thing. You're absolutely right! An instance (server) can have a bunch of different local communities, and each other instance on the fediverse can as well. It's analogous to having a network of little Reddits, each with its own site-level admin staff and moderators who oversee the individual communities. Just like how admins on Reddit can take actions that overrule moderators, so can admins on each Lemmy instance overrule moderators of local communities. So, in short, a community is likely subject not only to its own rules but the rules of the Lemmy instance where it is hosted. This can become a bit of a headache if you're just starting out, as instances we're federating with will have their own rules, and so will the communities that reside on them. What is that, three layers of rules to keep in mind? It sounds like a lot, and it is, but I assure you that you get used to reading the rules as you go along. My best advice is to behave in a friendly (not hateful, mean, or abrasive) yet casual manner, and you are not likely to run into major problems.
So, I think that's a fairly comprehensive overview of how Lemmy works, at least from the perspective of a user. There are a lot of other smaller topics that are worth exploring, but I wanted to have a good Introductory chapter that got the heavy stuff out of the way first. You will probably have questions after this and may even run into issues. Feel free to message me, ask questions, or provide suggestions for further chapters like this.
Next Chapter: How to Subscribe to Communities
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