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.
Mostly phishing. Passkeys can’t be phished. And really, passwords are awful in general for security purposes. You don’t have to use your phone or google or apple or whatever.
I actually have a physical usb key that I use as a passkey. Its just a more secure login implementation and will likely be the only option in the future.