The OAuth Authorization Code grant is a widely used framework for securely managing user authentication and authorization, providing multiple tokens such as access, refresh, and optional ID tokens. These tokens are pivotal for gaining access to APIs and protected resources, with the access token being used directly, while the refresh token allows obtaining new access tokens. The FusionAuth team advocates for integrating OAuth standards, highlighting benefits like centralized personal information storage, granular user permissions, and advanced authentication functionalities like MFA and single sign-on. Tokens can be stored either on the client-side or server-side, each method offering distinct advantages; client-side storage enhances scalability for distributed applications, while server-side storage simplifies integration for monolithic applications. Token validation is crucial, with options like JWTs enabling signature checking, and introspection providing an alternative where tokens lack internal structure. The ID token, which should be securely stored and not used for accessing protected data, is primarily for displaying user information.