What is OpenID Connect?

OpenID Connect is an authentication layer on top of the OAuth 2.0 authorization framework. It allows clients to verify the identity of the end-user based on the authentication performed by an authorization server, as well as to obtain basic profile information about the end-user in an interoperable and REST-like manner. It's commonly used for Single Sign-On (SSO) implementations and to allow users to log in to different applications using their existing accounts (e.g., Google, Facebook, etc.).