A session can be defined as a server-side storage of information that is desired to persist throughout the user's interaction with the web application.
Instead of storing large and constantly changing data via cookies in the user's browser (i.e. CookieStore), only a unique identifier is stored on the client side called a "session id". This session id is passed to the web server on every request. The web application uses the session id as the key for retrieving the stored data from the database/memory. The session data is then available inside the session storage, memory or/and backend.
Example Code:
Look more at: https://github.com/get-ion/sessions/tree/master/_examples