In order for customers to pay using Apple Pay, a credit or debit card from a participating bank needs to be added to the Passbook application on a compatible device running iOS 8.1 or later. Apple Pay can be used at select stores that accept contactless payments at checkout.
Users who have an Apple Pay-supported credit or debit card stored in their iTunes account are automatically prompted to add their card to Passbook. If the user chooses to add their card to Passbook, the card's issuing bank then decides whether to allow the card to transact using Apple Pay.
Apple Pay works by implementing near field communication technology, which allows users to make purchases by tapping their phone on a payment terminal. When an NFC field is detected by an Apple Pay-compatible device, the user is presented with his default credit or debit card. In order to complete a purchase, Apple Pay requires the user to authenticate by using the Touch ID fingerprint scanner or a passcode.
Apple has heavily touted the privacy features built in to Apple Pay, compared to similar payment services. Notably, retailers supporting Apple Pay never have the ability to see a customer's credit card number.