If you want a product you've created to work with Amazon DevPay, you must register it with DevPay at some point before you go live with the product. Registration does not make your product visible to the world (you do that yourself when you advertise the URL where customers can sign up for your product). For complete information about registration, go to the Amazon DevPay Developer Guide.
For this example, all you need to know is that the registration process provides you with:
Purchase URL— A URL for a web page where customers can purchase your product
Product token— A token that identifies your product to AWS. It is a long encoded string prefixed with the literal string
You must embed the product token within the code of the product because the product token is used in subsequent requests to AWS.
For the purposes of this example, we'll proceed as if the registration process for the sample code is complete and the product token is already embedded into the sample code.
During product registration, you're also provided with a product code, but it's not needed for this particular example.