Short and simple - if u saw the barber pull out his customer
hair with a comb, holds it and cut it with the machine or usually
scissors, he's doing a "layered" cut where the hair remains dark in
colour but just gets thinner or slightly shorter
If he doesnt but using machine cutter straight on the head he is
doing a "style" cut like high slope, mushrooms, 2-finger slopes ect
where your hair show some "light colour or scalp skin" after the
cut. the shape of your head also changes