Here is a simplified description:

What are Zaps?

Learn about what Zaps are, how they work, and what you need to use them on your Nostr client.

Here is the protocol specification:

GitHub

nips/57.md at master · nostr-protocol/nips

Nostr Implementation Possibilities. Contribute to nostr-protocol/nips development by creating an account on GitHub.

Does that mean you could technically both agree to lie to everyone using a self created event using kind 9735 without ever sending sats? Is that what I'm reading?