Most cats have four basic types of hair:

Guard Hairs - Guard hairs are the most obvious hair on your cat and make up most of the outer top coat.  They are straight, slender and taper toward the tip.  Guard hairs are longer and thicker than either the down or awn hairs.  They protect the underfur from the outside elements and act as a waterproof outer jacket.  The cuticles of these hairs have microscopically small barbs that are very rough.  This is the main reason cat hairs stick to clothing. 

Awn Hairs - Awn hairs are the hairs that make up the middle of the coat of the cat.  These intermediate size hairs that have broken or cracked cuticles that are rough and are still part of the primary coat of the cat. Their multi purpose is to help insulate the cat and protect the down hairs below.

Down Hairs - Down hairs are the hairs that are the closest to the skin and form the undercoat of your cat.  They are short, soft and fine.  Just like a goose down feather comforter, they help keep the cat warm.  Although the hairs appear straight they look crimped or wavy if viewed under magnification.  The wavy effect of the hairs help trap in the air and help keep the cat insulated.

Vibrissae -  Vibrissae are the thicker hairs that are also known as wiskers on the muzzle.

Within the Persian breed there is a wide range of difference in the type of hair and distribution.