They are called clutch heads because they don't need downward pressure from the driver tip to screw them in- the driver doesn't jump when torque is applied, it "clutches" the screw. You need downward pressure to Phillips, slotted, and Filister. You don't for Torx, Robertson (square), hex/allen, and clutch. Clutch heads can stand a lot of torque without ripping out the slot.
