Sorry for my late reply, I was on the road!
As for your question -- it's totally understandable to be confused, because this part of Mastodon (the whole way instances-and-accounts work) is pretty confusing, or at least it confused *me* at the beginning!
The way it works is this:
- when someone signs up at an instance (also called a "server", means the same thing as "instance), they pick a user name. For example, I signed up at a server called "saturation.social", and I picked the user name "clive".
- so my Mastodon name became "@clive@saturation.social". It's a little bit like the way email addresses work, I guess? Anyway, if you type "@clive@saturation.social" into the search bar of your Mastodon software, you should find me and be able to follow me. And once you've followed me, you can click on my username in your Mastodon software and you should see all my posts
- there is another way to see what I've been posting on Mastodon! You could go the URL for my account. The way the URLs work is that mine looks like this: https://saturation.social/@clive ... if you go there it's like the web page of my Mastodon account
- sometimes people might have a few different accounts at different Mastodon servers. For example, if you search for "Clive Thompson" you'll also see another account I have, @pomeranian99@fosstodon.org ... though I don't use it much any more. It's an older account from a few years back
- you are correct that a server (also sometimes called an "instance") can block another server. For example, if the people on my server, Saturation.social, decided that the folks on another server -- AggroTrollsOfMastodon.lol, for example (I'm making that up, heh) -- were a bunch of unpleasant trolls, we could just block AggroTrollsOfMastodon.lol. That would mean that nobody on AggroTrollsOfMastodon.lol could see any of the posts that people on Saturation.social write, and vice versa
I hope this helps a bit? It is confusing (I think it ought to be simplified, though I don't really know how) ... though one does get used to it reasonably quickly
