I see it as NOSTR is a decentralised Authentication layer. (The glue that sticks everything together)

Basically we create accounts on NOSTR which can then be used to sign in on any app or service that integrates with NOSTR.

The benefit is we keep our friends lists and anything else we tied to our Nostr identity through the different events and kinds when we log in to a new app.

That's about as far as I got with understanding it so far 😄