One mark on a paper and you have a composition! Every other mark, smudge, color, shape, pattern or form and on and on is then a component -- a part of the composition. A compositional sketch or "thumbnail sketch" is a small version of what you might choose to make into a larger drawing or painting. When you draw it small you can draw it fast and see how it feels. This is especially important in choosing the format or outer limits of your drawing or painting. When an artwork is completed -- and while you are working on it -- all parts are taken in by the eye to see the total composition.