OAuth (Open Authorization) is an authorization protocol, rather than an authentication protocol. It enables websites or applications (Consumers) to access Protected Resources from a web service (Service Provider) via an API, without requiring Users to disclose their Service Provider credentials to the Consumers.

More generally, OAuth creates a freely implementable and generic methodology for API authentication.

Azure OpenID Connect extends OAuth to include authentication capabilities, allowing secure user sign-ins for cloud applications.

Note: Post finalized using LLMs (chatgpt)