Helicopter rotors are large, rotating blades that provide lift and control for the aircraft. They work by creating differences in air pressure above and below the blades, allowing the helicopter to rise, descend, and maneuver in the air. The main rotor is typically located on top of the helicopter, while a smaller tail rotor helps stabilize and control the direction of flight. The design of helicopter rotors can vary, with some featuring two blades and others having multiple blades for increased efficiency. Materials used in rotor construction often include lightweight composites and metals to ensure strength and durability while minimizing weight.