Sketching pencils are a bit different, due to the fact they are generally softer, or at least have a wider range of hard to soft, allowing for lots of different finishes, and artistic possibilites when sketching. You can get them in ready made sets of pencils, with the full range in, or buy them individually for your own collection.
Sketching itself, is a classic form of art, whereby people use sketching pencils on paper to draw (sketch) landscapes, objects, people or anything else, creating an effect of graphite on paper which is instantly recognisable.