My NIP-05 is Jordan@acceptcrypto.org because I run a website called nostr:npub1nkhgdnemn6vmpnjsme54jxxdq4m7km74k4tc3rvmy8n72m7hnzwshfyg0p which is about encouraging, and promoting Bitcoin, and Cryptocurrency adoption for payments.

Bitcoin is a Cryptocurrency.

It is meant to be used as a medium of exchange but yes, you can also save it too.