Softer, 4-6B pencils are used for larger quick sketches or figure studies. The softer the pencil, the faster it will wear down and the more it will need to be sharpened. Soft pencils can produce good results shading but will not hold a point for long. White erasors are soft and good for general erasures while pink eraser types are generally harder and may damage soft papers. Pencil lines can be softened by rubbing gently with a stump or tortillon that are paper or cotton fibers molded to a wide point.
Pastel pencils have pastel incased in wood for use in detail work.
Colored pencils can be wax based or watercolor based and have color pigments instead of graphite as a 'lead'.