Sorry I massively oversimplified because I think it's a big picture issue. Of course there is a lot of grey. But essentially there are currently three big picture models. There's one big database (which of course is not really one db, but again simplifying) aka Twitter, there's semi decentralized where independent servers federate aka mastodon, and there's fully decentralized like nostr currently is trying to be for the most part.

I'm not trying to be dismissive or sarcastic. I've tried to come up with something better and I can't. But that doesn't mean someone else couldn't. Maybe you will. I hope you do.