A token is a collection of identity information that goes from one system to another. A token may consist of a user’s email and password, and data about the system that is sending the information.
An example of a token is the way Google manages access to the products in G-Suite. Once you sign in to your Gmail, you get access to other applications, like YouTube, Google Drive, and Google Photos, without having to log in again for each app.
The token ensures you will gain access to multiple systems without needing to remember different credentials for each one.