What's new in Apple Pay
... payments, right on iPhone — without any extra terminals or hardware.2 Merchants can use your app to accept payment using Apple Pay, Apple Watch, contactless ...
https://developer.apple.com/apple-pay/whats-new/Apple Pay | Apple Developer Documentation
Apple Pay is a secure, easy way to make payments for physical goods and services — as well as donations and subscriptions — in apps running on iPhone, iPad, ...
https://developer.apple.com/design/human-interface-guidelines/apple-pay