Imagine trying to tell your friends how to find your Nostr account by sharing your npub. It gets clunky really fast.

So instead, what if you could share an email address that's easy to remember, and if they type that into their client, they can easily find and follow you?

That's essential what NIP-05 allows you to do. The site you use for your Nostr identity will translate your address into an npub so that people can easily find you.

It also provides a layer of validation that you either are who you say you are, or you're a real person to begin with (most bots don't bother setting up NIP-05 identities). And most clients will give you a nice little check by your name if you have a valid id.