Quote:ASP.NET session state enables you to store and retrieve values for a user as the user navigates ASP.NET pages in a Web application. HTTP is a stateless protocol. This means that a Web server treats each HTTP request for a page as an independent request. The server retains no knowledge of variable values that were used during previous requests. ASP.NET session state identifies requests from the same browser during a limited time window as a session, and provides a way to persist variable values for the duration of that session. By default, ASP.NET session state is enabled for all ASP.NET applications.
The types of session in ASP.Net:
*In process:The session with in application domain under workprocessor is called in process session. The session out side app domain external to workprocessor is called out process session. the external process for maintaining session can be
*custom(accomplished by manual coding)
Well for more info about sessions please visit this link