Variation on a Pencil
Pencils are made from a mixture of graphite and clay. By varying the ratio of graphite to clay, pencil makers can adjust the "hardness". They have numbers indicating how Hard (H) or Black (B) they are. The range starts from 9H (very hard) to HB (medium) in the middle down to 9B (very Black and very soft) or even BB.
Scale:  9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, 1H, HB, 1B, 2B, 3B, 4B, 5B, 6B, 7B, 8B, 9B, BB

An ideal starting pencil is a 2B, this is soft enough to use for general use, Hard pencils are made for technical drawing and so unsuitable for artwork.

Solid Graphite Pencil /
These are solid graphite sticks without the wood, the same width of a pencil.

Propelling Pencil & Clutch Pencil
These grip very thin lengths of lead. The Propelling pencils are approx. 0.5 mm wide and the lead protrudes in stages as you press down on the top of the pencil.
The Clutch pencils are approx. 1mm wide and release the lead when the top of the pencil is depressed.

Water Soluble Pencil
These are fairly wide pencils which can be used dry and sketched in the normal way on dry paper, then apply a light wash with a brush.

Charcoal
Charcoal is made from smouldering willow twigs, as it produces a wide dark tone it is ideal for use in life drawing or large drawing area's in which you can work fast and bold.  It can be blended very easily with your finger or a stump of rolled paper.

Charcoal Pencils
Charcoal Pencils are compressed Charcoal formed into a thick pencil, these produce a dense black tone which is not so easy to remove with an eraser.

Carres
Are hard compressed pastels (square) produced in a variety of tones, Black, White, Sanguine, Terracotta etc.

Note:
Most of the above materials especially Charcoal can smear easy when touched and so needs to be fixed with a fine layer of aerosol fixative.

Making a Pencil

1. Pencil Blocks are cut into "Pencil Slats."
2. Pencil Slats are treated with wax and stain.
3. A machine cuts grooves into the slats to accept the writing core (or "lead").
4. Cores made from a mixture of graphite and clay are placed into the grooves.
5. A second grooved slat is glued onto the first - making a "sandwich."
6. The sandwich is machined into pencil shapes.
7. Individual pencils are cut from the sandwich, and are sanded smooth.
8. Each pencil is painted.