Session state

Server-side Session state is held by a collection of user-defined session variables that are persistent during a user session. These variables, accessed using the Session collection, are unique to each session instance. The variables can be set to be automatically destroyed after a defined time of inactivity even if the session does not end. Client-side user session is maintained by either a cookieor by encoding the session ID in the URL itself.^[6]

ASP.NET supports three modes of persistence for server-side session variables