The OAuth protocol 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.
An example use case is allowing printing service printer.example.com (the Consumer), to access private photos stored on photos.example.net (the Service Provider) without requiring Users to provide their photos.example.net credentials to printer.example.com.
Authenticating with OAuth
OAuth authentication is the process in which Users grant access to their Protected Resources without sharing their credentials with the Consumer. OAuth uses Tokens generated by the Service Provider instead of the User’s credentials in Protected Resources requests.