This is a form of single sign on authentication. User can use existing details from a social networking instead of make an account for specifically for the website as well as this method use...
Token-Based Authentication. This method uses tokens to authenticate users instead of cookies. The user authenticates using valid credentials and the server returns a signed token.

Common Authentication Methods for Web APIs. API Keys:API keys are unique identifiers issued to developers or clients.

Site authentication can range from classic username-password combinations to more advanced biometric and hardware-based solutions.Common Website Authentication Methods.

Biometric authentication methods. Fingerprint authentication uses an individual's unique fingerprint to verify their identity.
Todays article separately discloses secure authentication methods & website authentication protocols. And along with what they are.