What is the use of tail Blade in Helicopter

The Tail Rotor :
The tail rotor is very important. If you spin a rotor using an engine, the rotor will rotate, but the engine and the helicopter will try to rotate in the opposite direction.

This is called TORQUE REACTION.

The tail rotor is used like a small propeller, to pull against torque reaction and hold the helicopter straight.Without the Tail Rotor, the Helicopter will start rotating in the direction opposite to that of the mail Rotor once it takes off.

It's enough to destory the small tail rotor to crash a big Helicopter.