Hey Stephen, welcome to the fediverse!
Mastodon works pretty similarly to Twitter, in the sense that you’re microblogging. The biggest difference is that you can follow people who are on other servers - I’m writing to you from my instance at social.deadsuperhero.com, but both of us are experiencing this interaction as though we are in the same place.
Think of it like blog syndication, like RSS, but your subscribers can reply back to you, and you can see what they have to say.