Model-View-Controller(MVC) pattern is one the most popular pattern in all the ages of Object oriented technology.



As the name says MVC differentiates Model, View and Controller. The term model stands for the entity(or static data)- typically Database or files. The term View stands for User Interface or interaction with external system. The term Controller stands for the traffic policeman standing in middle.



Seperating M,V and C will give higher degree of clarity to the system. Take a scenario wherein you want to web-enable your client server application. In a typical MVC architecture, only the View gets affected.



Now a typical question arises, where the business logic resides? MVC has different explanations to this over the past 2 decades. From the age of smalltalk till the J2EE this part keeps changing. But keep in mind the basic idea of MVC is to seperate your M,V & C



This is just a high end briefing of MVC and MVC as such is a big topic.

It is an architectural pattern to separate the business model from the user interface.

There is much material available on this subject. See http://www.google.com/search?q=model+view+controller