The Basic Parts of Helicopters (Rotor Wing)

The basic parts of a helicopter are the fuselage.tail boom,landing gear or skid,engines,vertical stabilizer(tail),horizontal stabilizer,main rotor and tail rotor guards etc. The rotors are mounted on mast. 

Main Rotor: The main rotor has two or more blades. Each blade is an airfoil having a profile similar to that of an airplane wing. The main rotor is driven by the engines. The lift force is produced by aerodynamics action. The main rotor is subject to  a number of special conditions that must be given consideration to evaluate a helicopter. The rotor blades are subject to centrifugal force,gyroscopic procession,torque etc.

Tail Rotor: The tail rotor is small rotor mounted at the end of tail boom. According to Newton's third law of motion for every force there is equal and opposite force. To counter act the torque force produced by the main rotor,the tail rotor produces equal and opposite the torque force in opposite direction. Without the tail rotor the helicopters would keep rotating unless the corrective measures were taken,similar reaction would occur if the tail rotors fails in the flight. 

The Tandem rotor and Co-axial rotor helicopters use two synchronized rotors rotating in opposite direction. The opposite direction of the rotors causes the one to cancel the torque of other rotor,thus eliminating the need of the tail rotor.