Sketches drawing can be made in any kind of drawing medium. This term is most often used to graphic work executed in a dry medium such as silverpoint, graphite, pencil, charcoal,pastel. But it may also apply to drawings executed in pen and ink, ballpoint pen, water colour or oil paint. The latter two are generally referred to as "water colour sketches" and "oil sketches.
Sketching someone or is generally a kind of part of the studies of art students. This generally includes making sketches from a live model whose pose changes every few minutes you have to stick with your mind before start a sketch. A sketch usually implies a quick and loosely work, while related terms such as study, modello and "preparatory drawing" usually refer to more finished and careful works to be used as a basis for a final work, often in a different medium, but the distinction is imprecise. Underdrawing is drawing underneath the final work, which may sometimes still be visible, or can be viewed by modern scientific methods such as X rays.
As under you can look and stare at this make different phenomina ,in such paintings there is a story behind. every pwerson will look this painting in his shape of view.
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From @lays