What is the difference between OAuth2 and OpenID protocols for authentication and authorization?

OAuth2 and OpenID Connect are protocols that are often used together but serve different purposes:

• OAuth2 is an authorization protocol. It allows applications to obtain limited access to a user's resources on a server without sharing the password. OAuth2 is responsible for issuing access tokens that grant permission for specific actions.

• OpenID Connect (OIDC) is an authentication protocol built on top of OAuth2. It allows an application to verify the user's identity by providing an ID token containing user information (such as email, name).

In simple terms:

• OAuth2 is responsible for permissions (authorization).
• OpenID Connect is responsible for identity verification (authentication).

For example, if you want a user to log into your application via Google, you use OpenID Connect to obtain user information, and OAuth2 to access their data (like calendar) with their permission.