The document discusses the Model-View-Controller (MVC) architectural pattern used in ASP.NET applications. It describes the three main components - the model, which manages the application's data logic; the view, which displays the user interface; and the controller, which allows manipulation of the view. It provides an overview of how these components are implemented in ASP.NET MVC and the advantages it provides such as testability and separation of concerns. Potential problems discussed include difficulty testing GUI code.