an NPUB is a cryptographic address

Here’s your NPUB: nostr:npub1v04weqdvqhe2flgpwf7hhztfqpp0xr8drd5mea4q2vlvrcwdl7lqfa08ph

you also have a more human-readable name which we call a NIP-05:
markola@nostrplebs.com

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a little more detail since your avatar mentions bitcoin:

you know how in bitcoin you can just setup an address to receive bitcoin and you don’t have to rely on any central authority (e.g. JP Morgan/Chase, Bank of America, Coinbase, etc.) to setup a bank account or address or anything? this is kind of what an NPUB is trying to achieve, but for an Internet identity. Setup an identity (for social networking or maybe even another purpose) without having to ask a central authority (Facebook, Instagram, Twitter, etc.) for permission.

Obviously the NPUB is kind of ugly and a hassle to explain to someone orally. So a NIP-05 is an identifier you can register to make it easier to explain to someone. But note, when you use a NIP-05 you’re relying on whoever owns the domain (in your case the owner of nostrplebs.com) to agree to let you exist.

NPUBs don’t require anyone to issue/agree to your identity. You just do math and have it. NPUB is a public key. NSEC is the private key that corresponds to your NPUB.

I found your NPUB and your NIP-05 on your profile. Different nostr clients may emphasize/hide these features depending on their goals.