Passkey is some sort of specific unique key to a device allowing to use a pin on a device instead of the password. But which won’t work on another device.
Now I don’t know if that key can be stolen or not, or if it’s really more secure or not, as people have really unsecure pins.
Both the website and your physical security token must support the right type of webauthn credentials (the token has storage for a certain number of slots with “discoverable credentials”).
Passkeys is a variant of the same which is bound to your device’s own TPM / SE security chip or equivalent, plus a synchronization feature for backups.