Laser hair removal is, technically speaking, epilation by laser or with the use of a special light. Besides the body, certain types of laser hair removal may safely be used to reduce facial hair as well. The laser (or light) of a particular wavelength is used to cause damage to dark elements in hair follicles. These elements are referred to as chromophores. They can be artificially produced or naturally occurring.
Today, most techniques target naturally occurring chromophores, in particular, melanin. Melanin gives colour to both hair and skin. Of the former, there are two types: eumelanin and pheomelanin. Eumelanin gives a brown or black colour. The latter gives a blonde or red colour. Since the dark matter in hair follicles are the target, only the former - darker - type of hair is suitable for this procedure.
While laser hair removal became a commercial cosmetic procedure about 10 years ago, it has been experimented with well before then. In fact, medical lasers have been used to remove dark spots, acne scars, other types of skin blemishes and even tattoos. The point about laser hair removal is that, it's not permanent. In fact, in countries like the U.S., the FDA prohibits the advertisement of FDA-approved laser treatments to be described as a method of "permanent removal". Hence, use of the term "permanent reduction" or laser hair reduction to describe the procedure.
A more realistic description of laser hair removal is the "permanent reduction" of hair. It should be noted that, it's sometimes required to have multiple sessions of laser treatment over a certain period of time to achieve this goal. There is also no guarantee that ALL of the hair in the area treated will be reduced. To actually guarantee genuine permanent hair removal is to risk genuine scarring.
Ideally, the first thing the individual should do is to consult a qualified dermatologist. They should be able to advise on the suitability of the procedure. In any event, results will be most noticeable on light skinned individuals with dark hair. A lot more care will need to be taken, if the procedure is done on darker skinned and/or tanned individuals.
What you should be careful about
As noted above, one is well advised to avoid establishments that make false claims. The following are some of the more popular ones:
There is absolutely no pain or it's virtually painless. It is for many without needing any relief from the pain, but not for everyone.
The safe, permanent removal of hair. Again, the safe goal is hair reduction. Permanent removal is possible with scarring.
No re-growth of hair whatsoever. To date, there has been no real, genuine, qualified and objective evidence to support this claim.
It's "laser electrolysis" or "lasertrolysis". Hair reduction via electrolysis is completely different from reduction via the use of a laser. Both have their pros and cons, in terms of suitability and effectiveness.
In the end, it's best to consult a qualified dermatologist first.