Apple Pay
Apple Pay is a secure, easy way to make payments for physical goods and services—as well as donations and subscriptions—in iOS apps, in watchOS apps, and on websites. People authorize payments and provide shipping and contact information, using credentials that are securely stored on the device.
TIP It’s important for app developers to understand the difference between Apple Pay and In-App Purchase. Use Apple Pay in your app to sell physical goods like groceries, clothing, and appliances; for services such as club memberships, hotel reservations, and tickets for events; and for donations. Use In-App Purchase in your app to sell virtual goods, such as premium content for your app, and subscriptions for digital content.
Apple Pay in Apps
Apps that accept Apple Pay display an Apple Pay mark wherever available payment options are shown and an Apple Pay button that people tap to bring up a payment sheet. During checkout, the payment sheet can show the credit or debit card linked to Apple Pay, purchase amount (including tax and fees), shipping options, and contact information. People make any necessary adjustments and then authorize payment and complete the purchase.

For developer guidance, see PassKit > Apple Pay.
Apple Pay on the Web
Websites that accept Apple Pay incorporate it into the purchasing flow. An Apple Pay mark should be shown wherever available payment options are shown and an Apple Pay button can be clicked to bring up a payment sheet. During checkout, the payment sheet can show the credit or debit card linked to Apple Pay, purchase amount (including tax and fees), shipping options, and contact information. People make any necessary adjustments, authorize payment, and complete the purchase using securely stored credentials on an iPhone, an iPad, or a MacBook Pro with Touch ID. On other Macs, the purchase is confirmed with the user's nearby iPhone or Apple Watch that has Apple Pay enabled.
All websites that offer Apple Pay must include a privacy statement and adhere to the Apple Pay on the Web Acceptable Use Guidelines. For developer guidance, see Apple Pay on the Web. For a hands-on demo of Apple Pay on the web, see Apple Pay on the Web Demo.