Pay for Stuff With Your iPhone
The iPhone 8 and iPhone 8 Plus support Apple Pay and Apple Pay Cash. This allows you to use your phone to pay for stuff in stores, at vending machines, on the web, in apps and even send money to friends.
Most major banks support Apple Pay, which will put a virtual credit card or debit card in your iPhone. You can tap to pay at many stores, even if you don't see an Apple Pay logo.
Apple asks you to set this up when you setup the iPhone, but if you skipped or need to add another card open the Wallet App -> Tap the plus icon -> Tap Continue -> Tap Add Card -> Use the camera to scan your card. Verify the card if required and accept the terms.
Now you can make a payment at a store. You can also setup Apple Pay Cash and use that to send money to friends or use that card to make payments in a store.