It works like an iron, instead of ironing your clothes and making them straight you iron your hair! GHD are the best as they are not damaging to the hair
Can I just say that I don't wanna row about it but ghd straightners are just as bad as any other make of ceramic straightner. Sorry. If you want to keep your hair protected from heat and styling damage a spray is available in the usual high street shops. Usually called heat seal or something along the lines. But this won't necessarily stop all damage...
it works by breaking hydrogen bonds in the tertiary structure of the alpha chain, (hair is made up of microfibres and macrofibrils, which in turn are made from alpha and beta chains) this allows you to apply heat and then to re-set your hair from wavy into straight