In authentication, we usually look for the following factors to verify the user identity `something I know, something I have, something I am.` In passkey, theoretically, you verify all the factors at once. This user has the phone, and the biometrics said, `something I have.` The `something I know` was verified once to create a continuous of the other factors. If you lose your phone, you need to find an alternative way to verify the other factors, which can be done by various methods that each authentication provider has.