This new option for Apple Watch users is intended to make it easier to pass through Transportation Security Administration (TSA) checkpoints at participating airports. According to Apple’s announcement, airports that are taking part in the program will have specific checkpoints and lanes set aside to accept IDs via Apple Wallet.
Apple
When available, you'll be able to add your State ID to your Apple Wallet in a similar way to adding a credit card. You'll need to scan your ID card, take a selfie, and perform a series of facial and head movements for added security.