Definition: A Token is an information security hardware device that is in the possession of a user. The implement is primarily used for authentication and is associated with “something that a user has”.
The security token is used as one part of a multi-factor authentication (recommended by security experts). Some even randomly generate a one-time access number to be entered into the system. Others have electronic information recorded upon them and are read once the device is put into the appropriate access port.
Its Relevance: The token makes it possible for the third part of authentication to be fulfilled. The first is a "password". The second is a biometric component and the third is a token (or something that the user must possess).