With helicopters torque provides the spinning action of the main rotor. The spinning of the rest of helicopter is the "equal and opposite reaction" known as torque reaction. When the main rotor on a helicopter spins the rest of the helicopter will try to spin as well -- in the opposite direction. The tail rotor -- that smaller set of blades on the tail of the helicopter -- is used to counteract the torque reaction and keep the body of the helicopter from spinning around and keep it from drifting.
Airplanes can also have a noticable torque reaction. As the propellers spin in one direction creating torque, an equal force on the wings attempts to rotate or spin the body of the airplane in the opposite direction creating a torque reaction. In some cases wing configuration, propeller size, and engine horsepower can be used to offset the torque reaction as well as the pilot's use of the rudder.
