Sessions are basically server variables that are used to store information on Server.
Session in ASP.NET enables you to store information on server & access that stored information on your sub-sequent web-requests.
HTTP is a stateless protocol, it means every web-request is a new web-request in itself. It does not hold or preserve previous request data. So, Sessions provides us a way to identify the user from on the subsequent web requests.
How to set a value in session in C#:
Session["Email"] = "firstname.lastname@example.org";
How to retrieve the stored value from the session:
string email = Convert.ToString(Session["Email"])
I have covered only basics. You should also study below advanced topics related to Session: