Apple Pay is a digital wallet from Apple which lets you use a compatible iPhone, Apple Watch or iPad to make secure contactless purchase in stores, within selected apps and participating websites.
Other helpful FAQs.
Apple Pay works with iPhone 6 and later in stores, apps, and websites in Safari; with Apple Watch in stores and apps; with iPad Pro, iPad Air 2, and iPad mini 3 and later in apps and websites; and with Mac in Safari with an Apple Pay enabled iPhone 6 or later or Apple Watch. For a list of compatible Apple Pay devices, see https://support.apple.com/km207105
No, your card details are not stored on the device or in the Cloud. When a card is added to Apple Pay, a Device Account Number replaces the need for the card number.
The Device Account Number can be found by opening the Wallet app and tapping the (i) symbol in the bottom right corner and then scrolling down to find Device Account Number.
No, it does not cost you anything extra to use Apple Pay.
The usual credit or debit charges apply to purchases and some retailers may apply a credit or debit card surcharge to purchases made using any payment method, including Apple Pay, contactless or chip and PIN transactions.
You require an active data plan or Wi-fi connection to add your card to Apple Pay. Based upon your mobile plan and network, additional message and/or data charges may apply.