What is meant by proportional drawing?

First you have to measure the object you want to draw. You should compare two parts of the object, such as height and width as in the width of a glass versus its height, or how many times a small part of the object fits within a larger part, such as in the human body and the head. The smaller part should be the measure unit you use to compare to the bigger part. Then you decide the size you want to give the object in your drawing. You make a draft of the object's contour. You measure your drawing's width versus its height and decide if the scale coincides with your model. If it does, then you add the details.