The kick-down feature is designed to give maximum acceleration.
When the accelerator pedal is pressed right down past the point of resistance at full throttle, the gearbox will select a lower gear ratio, depending on road speed and engine speed. While you keep the accelerator depressed the engine speed is automatically controlled to give your vehicle maximum acceleration.
WARNING!
Please note that if the road surface is slippery or wet, the kick-down feature could cause the driving wheels to spin, which could result in skidding.