An Apple Wallet pass is a signed .pkpass archive rendered inside the iOS Wallet app. It carries a barcode (usually QR or PDF417), visual styling, and optional location- or time-based triggers that surface the pass on the lock screen.
Visitor management tools issue .pkpass files so a guest can keep their access credential on their phone instead of having to dig through email on arrival.
Apple Wallet passes are signed by a certificate tied to the issuing organization; passes cannot be forged without that certificate.