The main purpose using MVC pattern is to decouple the GUI from the Data. It also gives the ability to provide multiple views for the same Data. MVC pattern separates objects in to three important sections:-
1. Model: - This section is represented by Data view, Dataset, Typed Dataset, Business components, business entity models etc. Now this section can then be tied up to either windows application or web UI.
2.View: - ASPX, ASCX, or windows application UI like data grid etc. form the view part of it.
3. Controller: - In ASP.NET the behind code is the controller. As the events are handled by that part. Controller communicates both with Model as well as view.
I hope I was able to map you imagination of ASP.NET with the diagram given below.