OpenID Connect (OIDC) is an authentication layer built on top of the OAuth 2.0 protocol. It allows users to log in to different applications using a single set of credentials, enhancing user convenience and security. OIDC provides a standardized way for applications to verify a user's identity and obtain basic profile information. With OIDC, users can authenticate through a trusted identity provider, such as Google or Facebook, which manages their login details. This reduces the need for multiple usernames and passwords, making it easier for users to access various services while maintaining control over their personal information.