The word "cashmere" refers to the type of fleece that all goats, except Angoras, grow for their winter undercoats. "Cashmere goats" are simply goats that have been bred to produce more of this fleece than their counterparts, who have been bred for milk or meat production. There is no "cashmere" breed of goat, and thus, no registration of "pure bred cashmere goats". Goats that produce more of the cashmere fleece have been bred from all sorts of different breeds of goats, but mainly the larger, meat goats so that each animal will be big enough to produce a decent amount of fleece. Since the bloodlines of the goats bred for cashmere fleece production are so varied, progeny tend to be less predictable in color and other attributes than pure bred goats of the recognized breeds. Individual breeders may offer "registration" forms for their own bloodlines of cashmere goat stock, but there are no nationally or internationally accepted standards for the cashmere fleece producing animals. Goats shown as "cashmere" are judged on standard healthy goat conformation and handling criteria. The quality of the cashmere fleece is judged entirely from samples of fleece by fleece judging businesses.
Another aspect of the multi breed background of the cashmere producing goats is that these goats tend to be hardier than pure bred "breed" goats. That, plus their thick coats, makes them ideal for cold climate culture.
A good cashmere fleece producing goat will grow a thick layer of undercoat with relatively few guard hairs sticking out beyond the edge of the undercoat. That soft, furry undercoat will grow all the way down to just above the goat's knees, up the neck and even onto the cheeks, and all the way to the tail on the rump. The best cashmere fleece has the longest individual fibers (not guard hairs) and is naturally kinked the tightest. This fleece grows on the mid side, mostly, but can still be good onto the shoulders and toward the hips. The shorter fur of the neck and cheeks is useful to mix with other fibers to provide them more kink and softness. The coarser fiber from the rump and belly can be used for felting or rug making.
My own personal experience leads me to prefer combing fleece out rather than having the goats sheared. Cashmere producers with large herds of goats shear their goats. It's simply more cost effective.