OAuth 2.0 is an authorization framework that allows an application to access another service on behalf of a user, without needing the user's login credentials. This separation of roles between client and resource owner provides improved security by reducing the risk of password exploitation and minimizing the need for users to change passwords across multiple services. The OAuth 2.0 flow involves redirecting the user to an authorization server, where they grant access to the application, and then exchanging the authorization code for an access token that can be used to make requests to the protected resource. A refresh token is also obtained, which can be used to obtain a new access token when it expires. Implementing OAuth 2.0 correctly is crucial for user security and involves storing sensitive credentials securely and managing tokens carefully. The Authorization Code Flow is the most common variation of OAuth 2.0 that developers will encounter in practice, and by understanding this flow, building a mental model of it, and seeing practical examples, developers can implement OAuth 2.0 confidently for their own application use-cases.