A security token is a physical device used for authentication, often in conjunction with other authentication factors such as passwords, as one factor in a multi-factor authentication system. A security token may, among other things:
- provide a time-synchronized, continuously changing password (such as RSA SecurID)
- plug into a computer, containing digital certificates that are used along with a PIN for authentication (such as a USB dongle) or otherwise serving as an identifying device (such as a smart card)
- be a mobile device (such as a smartphone) with an app that implements one or more features used in traditional security tokens
For more information on security tokens, see this Wikipedia article.