Authentication tokens are digital keys used to verify a user's identity when accessing a system or application. They are generated after a user successfully logs in and serve as proof that the user has been authenticated. These tokens can be temporary or long-lasting, depending on the security requirements of the system. Tokens often come in various forms, such as JSON Web Tokens (JWT) or OAuth tokens. They help enhance security by allowing users to access resources without repeatedly entering their credentials. This reduces the risk of exposing sensitive information while maintaining a seamless user experience.