MVC is a very well defined and understood concept in computer science these days. If you're unfamiliar with MVC, I suggest you get reading :)
So, I expect you've used MVC whilst building applications, you have your controllers, models and views, all looks good. Whilst this is a great start, and allows you to separate control from data from presentation, the problem is most developers stop there and thing that is the end of the road. Below you can see a representation of a simple MVC triad: