Model View Controller architecture aims to separate an application into three parts:

Model: It is the business logic of an application. From an object oriented perspective it would consist of a set of classes that implement the critical functionality of an application from a business point of view.

View: It can consist of every type of interface given to the user. In ASP.NET the view is the set of web pages presented by a web application.

Controller: This part of the architecture is the most difficult to explain, hence the most difficult to implement in many platforms. The controller is the object that allows the manipulation of the view. Usually many applications implement Model-Controller tiers that contain the business logic along with the necessary code to manipulate a user interface. In an ASP.NET application the controller is implicitly represented by the code-behind or the server side code that generates the HTML presented to the user.