Wide Screen Monitor question

I am considering a LCD wide screen monitor. There is something that I don't understand. Granted that the aspect ratio of a standard monitor is not the same as a wide screen.
What changes occur in order to make the image show in wide screen? What I mean is, does it lop off some of the top and bottom? If not, where does tha image come from to fill in the sides? I am especially interested in, for instance what happens in the cockpit view.
What changes occur in order to make the image show in wide screen? What I mean is, does it lop off some of the top and bottom? If not, where does tha image come from to fill in the sides? I am especially interested in, for instance what happens in the cockpit view.