Hello friend, please note that session is not any page specific object, rather it's stored in the server. So, if you keep any value in a session object, that value can be accessed from any page with in the application until the session is expired.
For example, there in an application with 100 pages. Any session object will be accessible from all pages.
Session["Name"] = "Chander Rani";
string name = Session["Name"].ToString();
Note: It's a best practice to have a null check before accessing any session object.
I would suggest you to go through some online tutorials relates to Session object. Hope that would be helpful.