To use a different analogy from the commonly used email one, think of each instance as a country.

You are in your country, but that doesn't mean you can't hear about stuff from other countries.

Sometimes though, a country does something bad and becomes embargoed by your country. If this happens you can't hear about stuff from the country your country is embargoing.

By default you can hear about stuff from all countries (federation)

A country can become embargoed (defederation)

In each country, there are towns. And towns in different countries can have the same name. When you're looking at all the countries together this means you might want to listen to London UK and London USA.

A town can be considered a community in Lemmy, which is a subreddit in Reddit.

I just made this up so there's likely to be some flaw in the analogy but I think it helps give you a good sense.

Anything in particular that's troubling you? I've found most people here are really positive and will try to offer advice. I'm not really tech savvy, but if you've got any questions, I'll try and help.

Think of it as people using different email clients. When you're using Gmail, that doesn't stop you from emailing people on Yahoo or Hotmail right? It's the same with lemmy. Here people signup on different servers and you can talk to them. Think of it like a twitter user liking an Instagram post without leaving twitter. They can follow any Instagram user and see their posts if they follow them but they don't have to log into Instagram. And that's what Meta is trying to do with threads.

I appreciate you saying that your lost cause I also find lemmy confusing and it seems like most people here are very tech savvy. Makes me feel a little less out of place.