The honest answer is it's not completely permanent in the way that word usually implies, but it's called 'permanent hair reduction' for a reason. What the laser does is destroy the hair follicle or at least damage it enough that hair grows back much thinner, finer, and slower than before. Most people who complete their full series of treatments end up with little to no visible hair in the treated area. Some hair might regrow over many years, but it's usually minimal and much finer than original growth. Plus, you can always do maintenance sessions if needed, usually just once or twice a year if anything comes back.