MVC is short for Model View Controller and is a three layer pattern
for isolating busines logic from user interface. The user interacts via a user interface. the controller then handles these inputs and directs them to the model.
The model (ie the application or part of it) manages its data and displays it to the user via views. An IDE for instance holds source code and displays it via a text editor. It may also have file views (showing all files), class views showing all classes. The user interactions are passed as actions from the controller to the model and affect the views.
ASP.NET now has an alternative called MVC.