When you figure out the mechanics behind how something works (what goes into it, how it was formed, what is concept or main point) then the piece in its entirety is much easier to understand. It is almost like finding out a person history; if you figure out the history behind someone or something it makes it easier to understand. It also helps to look at other examples of what you are trying to do, that's why teachers let us look at sample works of 'A' papers so we know 1) what an A paper looks like so we have something to work up to and 2) we also see the mechanics of how an A paper is formed. All of these steps is what makes a good writer.