I just explained nostr to a bitcoiner as "a bit like wallet software and the blockchain"

Your profile and posts are like data on the blockchain. 

Nostr apps like  @primal or  @damus are akin to wallet software like Sparrow that serve up publicly accessible data.

Unlike Twitter or Facebook or IG, they don't own your account or data. They just create an interface that serves as lens through which to view YOUR data which YOU own (and the data of others, which THEY own).

They also package up data (i.e. new posts) into the nostr protocol and then "publish it to the blockchain" if you will.

Of course this data isn't hashed or linked the way blockchain data is.