The helicopter is one member of the very versatile family of airplanes known as VTOL, vertical take off and landing. The United States has used helicopters in military operations in every conflict, from Korea, to Operation Enduring Freedom and all  other engagements in between. The U.S. as well as other countries, use helicopters for non-military uses, including: air ambulances, air/sea rescue, heli-buses, and a host of other uses as well.

Although they look different, the helicopter and the airplane work in very much the same fashion, mind you not the same, but similar. On an airplane the air flowing over the wings provides the lift, on a helicopter the rotors take the place of the wings. Because, the helicopters rotors are so large, compared to the propeller props on an airplane, they cannot handle the high rpms, like the airplane props. So to solve this problem a system of gears was designed to slow the engine rpms down to a manageable speed.

Courtesy of www.travelnotes.de