In this screencast, the fifth installment of the Beginning iOS Development series, you will learn about windows, views, and view controllers.
View Controllers in the SDK
If you want to know more about the view controllers available in the SDK, check out the Interface Builder screencast, where an overview is given of all the view controllers available. If you want to implement a UINavigationController, check out this screencast by Axit on Mobiletuts+.
More information on MVC
Still hazy on what the MVC design paradigm is? There is a fantastic guide on Nettuts+ on what MVC is and how it is used in application development. This design paradigm extends into most programming languages and is not specific to iOS or Objective-C programming. The Nettuts+ tutorial discusses MVC in relation to web applications, but the same basic principles apply to iOS Development.