Authorization Grant Types are methods used in the OAuth 2.0 framework to obtain access tokens. These tokens allow applications to access user data securely without sharing passwords. The main grant types include Authorization Code, Implicit, Resource Owner Password Credentials, and Client Credentials. Each type serves different use cases and security requirements. The Authorization Code grant is commonly used for web applications, while the Implicit grant is suited for browser-based applications. The Resource Owner Password Credentials grant is used when users trust the application with their credentials, and the Client Credentials grant is for server-to-server communication.