What does the letters h and b mean on a pencil?

The letters "H" and "B" on a pencil indicate its hardness and blackness, respectively. "H" pencils are harder and produce lighter marks, while "B" pencils are softer and create darker marks. The scale ranges from H (hard) to B (black), with "F" representing a fine point in between. For example, a 2B pencil is softer and darker than an H pencil.