It is important to see writing an essay as a process. If you decided to build yourself a house, you probably would not begin by going to the lumberyard and loading your truck full of lumber, bricks, and nails. There is a lot of work to do before you get to this point, including the drawing up of plans for what you want to build and the determining of the building supplies that you will need. In a way, the same general idea applies to writing essays. We use the term "prewriting" to refer to the work you do on your essay before you actually begin writing a draft of it.