QR codes are two-dimensional barcodes that can store various types of information like URLs, contact info, and more. They work by encoding encrypted data that directs the user to a website, phone number, email, etc. when scanned by a smartphone camera. Originally used for tracking parts, QR codes are now commonly used in marketing. Some examples include boarding passes, paying at Starbucks via a QR code on your phone, and an interactive book that changes its QR coded content weekly. There are also developing applications in mobile marketing, customization, and gamification through QR codes. Considerations for using them include that the concept is still relatively new in the US and not all phones can scan them.