A wallet pass platform is software that runs a brand's wallet passes end to end. It designs passes, distributes them to Apple Wallet and Google Wallet, updates them, notifies pass holders, makes them readable at the till by NFC tap or QR scan, and integrates with CRM and POS systems.
Each of those jobs has real machinery behind it. Design means the layout, pass fields and images for each wallet. Distribution means add to wallet links, Google save links and often a hosted onboarding flow that creates the member as well as the pass. Updates differ by wallet: an Apple pass is a signed PKPass that the device fetches again from the pass web service after a push update, while a Google pass is a pass object the issuer rewrites through the Wallet API. Notifications ride on those updates as change messages on the lock screen. Identification covers barcodes and QR codes for any scanner, and Apple VAS and Google Smart Tap for NFC terminals. Integration is an API in and webhooks out, so a CRM or POS stays the source of truth.
The useful line to draw is between a platform and a pass generator. A generator produces a pass file once and its job ends when the customer saves it. A platform operates the pass for its whole life: it holds the certificates, answers the devices, pushes every balance and tier change, and retires the pass when the membership ends. The day-to-day difference is covered in pass lifecycle management.
When comparing platforms, ask whose accounts the passes are issued under: the Apple developer account that holds the pass type identifier, and the Google issuer ID. Those accounts decide who can update the passes already in members' wallets, and how easily the program can move later through a pass migration.