With a passkey you sign in without a password - using your device's biometric authentication or PIN instead (e.g. Face ID, fingerprint, Windows Hello).
Your device will ask for biometric confirmation or your device PIN. After that, the passkey is registered.
Click Remove next to a passkey in the list.
You can register separate passkeys for different devices. Each device gets its own entry in the list.
Passkeys are supported by modern browsers and operating systems. Make sure your browser and OS are up to date.