The tail rotor is a small, vertical rotor located at the rear of a helicopter. It is responsible for counteracting the torque produced by the main rotor, which would otherwise cause the helicopter to spin uncontrollably. The tail rotor generates thrust in a horizontal plane, pushing the helicopter's tail in the opposite direction to the main rotor's torque. This allows the helicopter to maintain directional control and fly in a straight line.
Here's a picture of a tail rotor:
[Image of a tail rotor]
