Sketching is generally a prescribed part of the studies of art students. This generally includes making sketches (croquis) from a live model whose pose changes every few minutes. A "sketch" usually implies a quick and loosely drawn 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.
HB pencil (good quality), 2B pencil, blue clour pencil (No compulsion)