Here are visual interpretations of ideas inside the head.
They don’t exist until you draw them. Eyes in a pea-pod turn into a punning ‘iPod’ on the left and, on the right, we can see a ‘drawing-tree’ and a ‘drawing walking stick’; not real life objects.
So - Drawings are visual ideas about form and space, about lightness and darkness.  They involve the measurement and the selection of things, observed or imagined. Drawings have a lot to do with trying to make sense of the world as we know it, and what we have seen, thought about, or remembered. They are ideas, thoughts and proposals turned into vision.