OAuth2 is an authorization framework that allows third-party applications to access user resources without sharing credentials. It is widely used for granting access to APIs while maintaining security and privacy. OAuth2 supports different flows such as authorization code, implicit, and client credentials, catering to various use cases. By providing secure and granular access control, OAuth2 ensures that users can authorize services without exposing their credentials. It is a key technology in modern authentication systems and is often paired with OpenID Connect for federated identity management.