Everything is awesome in slow motion -- and that includes laser hair removal.
In a video from Veritasium, they show what it looks like when hair is exposed to a laser.
Dark hair contains melanin, a pigment that protects us from ultraviolet light. Bursts of a high-energy laser are absorbed by the hairs more than the skin, and the hairs increase in temperature as they are exposed to the laser.
The hairs explode like popcorn as moisture evaporates from inside the follicle (scroll to 2:01 for the best example).
Eventually, the follicle is damaged to the point where cellular bonds break down during "denaturation." When enough damage is caused, the hair will not grow back.
Lasers can remove hair permanently or for several months, as the results differ for each person.