@ruthlessone @Lowie Dunno if this helps but I would put it like this:
1. Imagine a website where you can post things and other people on the site can read, share, and reply to those things. (like the bird site)
2. Imagine a bunch of different websites that do the same thing.
3. Now imagine that all those websites can exchange information with each other, so that while using one of them, you can read, share, and reply to things somebody else posted on a different one.
That's Mastodon in a nutshell. Each of the individual websites is called an "instance". And the whole collection of all the different websites that exchange information with each other is called the "fediverse". (Well there's more to it than that but the rest doesn't matter for purposes of this explanation)
All I know is that it works and that's good enough for me.