It’s called “just walk out” technology and when you walk out, your purchase is complete with a receipt in your app, charged to your Amazon account. This is achieved by an entryway that is similar to the subway turnstiles that you see in major cities. Yes this sounds like magic, retail magic.
A smartphone with the app installed is required to enter the store via presenting a barcode to a sensor. This barcode scan (along with other sensor technology eg: GPS, etc) tracks that you have entered the store, identifies you’re moving through the store and then identifies the product you pick up. To complete your shopping experience just walk out the door. Yes, that’s it. The image recognition combined with a sensor fusion of technologies has already confirmed your order and totalled it up. All billed to your future Amazon Bank Card, but currently to the payment card you have on file with them, the nearing 1 billion payment cards they have on file.