The PassSlot system generates an individual, unique pass based on an chosen template for every user that requests it. This has a major benefit that you don't have to pre-generate a fixed amount of passes as this was required when printing traditional passes. Passes can be generated by accessing a special template distribution URL (see the section called “Distribution of the Template”) or via the API. Every pass has an unique serial number so that you are able to keep track of every single pass. It is important to notice that even if the generated passes look the same, they are not really equal, they just have the same appearance, but different serial numbers (by default serial numbers are not directly visible on the pass).
With the use of the placeholder system every pass can be customized / personalized. This allows for much better user experience than with traditional paper passes where personalization was expensive. Further passes can be updated after they were generated, something that is not possible with paper passes.