The Model-View-Controller (MVC) architecture separates the modeling of the domain, the presentation, and the actions based on user input into three separate classes.
Unfortunately, the popularity of this pattern has resulted in a number of faulty usages; each technology (Java, ASP.NET, etc.) has defined it in their own way making it difficult to understand. In particular, the term "controller" has been used to mean different things in different contexts. The definitions given bellow are the closes possible ones I found for ASP.NET version of MVC.
Model: DataSet and typed DataSet (some times business object, object collection, XML, etc.) are the most common uses of the model.
View: The ASPX and ASCX files generally handle the responsibilities of the view.
Controllers: The handling of events or the controlling is usually done in the code-behind class.
In a complex n-tier distributed system the MVC architecture place the vital role of organizing the presentation tier of the system.
