An authorization server is a system that manages access to resources by verifying user identities and permissions. It plays a crucial role in security protocols, ensuring that only authorized users can access specific data or services. This server issues tokens that represent the user's permissions, allowing them to interact with various applications securely. When a user attempts to access a resource, the authorization server checks their credentials and determines if they have the necessary rights. If approved, it generates an access token, which the user can present to access the desired resource without needing to re-enter their credentials each time.