An access token is a type of credential used in authentication and authorization processes to verify a user's identity and grant them access to specific resources or actions within a system or application. It is a piece of data, often represented as a string of characters, that is generated and issued to a user after a successful authentication.

Access tokens are widely used in various digital systems, including web applications, mobile apps, APIs (Application Programming Interfaces), and more. They play a crucial role in ensuring secure access to protected resources and actions, and they help control permissions and actions users can perform within a system.

When a user logs into a system, the authentication process validates their credentials (e.g., username and password) and, upon successful authentication, generates an access token. This token is then provided to the user, allowing them to make authorized requests to the system or application.

Access tokens are time-bound and may have additional properties, such as scope, permissions, and other metadata, defining the extent of the user's access. Commonly, access tokens are used to authorize API requests, granting the necessary permissions for specific operations without requiring the user to share their credentials repeatedly.

Understanding access tokens is crucial for developers, security professionals, and system administrators involved in building, securing, and managing digital systems. Proper implementation and management of access tokens are fundamental to ensuring a secure and controlled access environment for users and applications.