Apple Passbook is a mobile application on an iPhone or iPod Touch that allows users to store .pkpass files called passes. Apple allows vendors to easily build passes that can be used as coupons, boarding passes, tickets, loyalty cards or gift certificates.
Passes can be distributed to customers through a browser, email attachment, SMS message or Passbook-enabled mobile app. Most passes are redeemable by scanning a barcode on the front of the pass or entering the pass's identification number with a keyboard on a computer or point-of-sale terminal.
Passbook, which was released by Apple with iOS 6, works with iCloud to keep a customer's passes up-to-date on multiple devices. When a device's location services are turned on, customers can be prompted when they are near a business they have a pass for in their Passbook folder.