Welcome to Nostr! 

Anything you post on one client (damus, primal amythest, etc) will be viewable on all other clients. And it gets better... your identity and history also follows you from one client to the next. 
The magic sauce is that Nostr is a protocol, not an app. 

Your Client (primal, damus etc) is used to read/write to the Nostr Protocol
Sorta like how your Browser (chrome, safari etc) is used to read/write to the Internet (TCP/IP) 

 So Cool 😎 thx for explaining it better