HTTP is a stateless protocol, it can’t hold the client information on page. In other words after every request and response the server does not remember the state, data and who the user was. If user inserts some information, and move to the next page, that data will be lost and user would not able to retrieve the information. So, Session provides that facility to store information on server memory.
Session("VALUE1") = s; //declaring session.
Also see below video to understand how ASP.NET page life cycle actually works.
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