OAuth 2.0 and OpenID Connect overview

OAuth 2.0 is an authorization framework that enables target applications (so-called OAuth 2.0 Clients) to securely obtain access to protected HTTP resources (such as user information) on behalf of a user. The obvious way to achieve this goal would be for the user to share her credentials (e.g. her password) with the target application. As sharing passwords has many drawbacks, OAuth 2.0 solves this problem without requiring the user to share credentials.

OpenID Connect 1.0 adds an identity layer to the OAuth 2.0 protocol, allows clients to verify the user's identity information and usually save a few HTTP roundtrips.