If you where to try and explain the Fediverse to someone, how would you explain it with it's different instances? As well as explain why it is better in some ways for the future of the Internet?
It's multiple social media sites that send each other messages to sync the content between them. You create your account on one of them, but you can see posts and can contact and follow people from all of them. They are run by different people, and if one goes offline or rogue the others preserve the content but stop syncing with it. So the sites keep each other honest, and no one person or company is in control of the whole thing.
It isn't very difficult to understand, or new. Usenet used a similar system of exchange between news servers, and before people had the Internet in their homes (pre- 1990s) BBS systems used RelayNet and FidoNet.