OAuth stands for Open Authorization. It is an open standard for token-based authentication and authorization.
OAuth provides client applications a “secure delegated access” to server resources on behalf of a resource owner.
Examples:
While creating MVC applications we might see the click here to login with external links such as Google, Facebook, twitter, Linkedin etc.,. So in order to use these external links, we need to authencate the users with third party resources, as they provide access in order to use their websites to login with our applications.
For more information please check on this link:
https://www.c-sharpcorner.com/UploadFile/26b237/building-mvc-5-application-with-an-open-authentication/