token
also: API token, auth token, security token, JWT
A token is a unique string of characters that authenticates or authorizes a user or application to access a system or service without needing a password each time.
In Linux systems, tokens serve as cryptographic credentials that prove identity or grant permission. They're commonly used in authentication (proving who you are) and authorization (proving what you're allowed to do). Unlike passwords, tokens are typically automatically generated, have expiration times, and can be revoked without changing a password.
Common examples include JWT (JSON Web Tokens) used in APIs, SSH keys that act as tokens for passwordless authentication, and OAuth tokens used by web applications. For instance, when you authenticate to a remote server via SSH key, that private key serves as a token that proves your identity without transmitting a password.
Tokens are also used in sudo sessions and API authentication. A process might receive a token like eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9... that it includes in requests to prove authorization to a service.