It's a Twitter clone with a smaller but higher quality community. If you liked Twitter you might like Mastodon. If you never liked Twitter, odds are you won't like Mastodon either.
IMO, it still suffers from the same lords-and-peasants system as Twitter since it's entirely follower based.
Taking the opportunity to plug my new favorite RSS app, Feeder. I found it recently from another Lemmy user. It's FOSS, no ads, beautiful, and has lots of features. Here it is on Google Play and F-Droid.
The instance owner/admins are in charge of that. They're kind of equivalent to the Reddit admins, except if you don't like the instance admins you can go to a different Lemmy instance but you can't move to a new Reddit instance. Also, community names are unique to each instance, so !support@lemmy.world and !support@lemm.ee share the same name but are two separate communities in two separate instances.
Ironically, this gives off an absolute unit of small dick energy