It is a NIP, but I can’t remember which one. 

You need a #Lightning wallet. Lightning is a second layer protocol on top of #Bitcoin.

As I believe you’re new to this, I’d suggest something simple like nostr:npub1hcwcj72tlyk7thtyc8nq763vwrq5p2avnyeyrrlwxrzuvdl7j3usj4h9rq to start with. It can be topped up with onchain (regular) #bitcoin, funds will be converted to sats on lightning network. Later if you want to withdraw back onchain, you can do it by simply sending sats to you bitcoin address.

You can connect the wallet in the settings of your Nostr client (app). This will allow you to send and receive #zaps directly to your wallet via Nostr.

See my #welcome guide for the best practices for a newcomer: https://habla.news/tony/welcome-to-nostr