It uses Nostr Wallet Connect (NIP-47) to authorize Damus to send payments using the connected wallet without leaving the app and without requiring confirmation on the wallet side for each payment. Damus uses the default zap amount you have set and gives you a few seconds to cancel the payment before it actually sends. The NIP mentions a spending quota so hopefully that’s implemented at some point. For now I’ve just created a separate wallet on Alby that’s only used for this and I keep the balance very low.

https://github.com/nostr-protocol/nips/blob/master/47.md?ref=blog.getalby.com