In the Webauthn context, there are two ceremonies:
The attestation ceremony: it corresponds to the registration of a new authenticator,
The assertion ceremony: it is used for the authentication of a user.
For both ceremonies, there are two steps to perform:
The creation of options: these options are sent to the authenticator and indicate what to do and how.
The response of the authenticator: after the user interacted with the authenticator, the authenticator computes a response that has to be verified.
Depending on the options and the capabilities of the authenticator, the user interaction may differ. It can be a simple touch on a button or a complete authentication using biometric means (PIN code, fingerprint, facial recognition…).