I'm sure you're on top of this but the quickest summary:

1. Not a blockchain (Bitcoin for payments is optional)

2. Own your identity and community. (public/private keys sign into any new Nostr based client or service that comes along and you bring in all your history and follows/ers )

3. Own your data. (Data is distributed among a number of relays that you trust, but its yours. Responsibility on you to back it up privately and to use relays that'll keep it available.)

4. Not just Twitter, but also basically any type of text based app we have today, just needs a client implementation for Nostr and all current apps can be replicated in Nostr. Discord (without voice), Reddit, Forums, comment sections on web pages, AOL chat rooms, anything, but it's all the same message content.