Both! Nostr is a protocol. Damus is an app that uses the protocol. Think of it like sending and email with Outlook or Gmail. Both of these apps use email protocols. Right now I'm talking to you on an Android app called Amethyst. Pretty cool, huh? 

 Yeah! Mad!! I only just heard of it tonight on a YouTube video, so I downloaded it, I need to get my head round how it works! ✌🏻 

 Oh that's awesome. What YouTube video did you watch if you don't mind me asking? 

 It was one about a photographer who’s left instagram and twitter I can’t remember the name