The dictionary defines a helicopter as an aircraft that flies by means of horizontally rotating blades. It is derived from the Greek words helix, meaning spiral, and pteron, meaning wing. Helicopters may be used for military or civil purposes, including transportation of troops, infantry support, firefighting, business transportation, medical purposes and police surveillance.

Aviation pioneers like Jan Bahyl, Louis Breguet, Emile Berliner, and Igor Sikorsky designed the first successful helicopters, with Juan de la Cierva introducing the first practical autogiro in 1923, which became the platform for the modern helicopter. Ral Pateras de Pescara, an inventor from Argentina, demonstrated the first fully controllable helicopter using special controls. The first practical helicopter, built by German inventor Professor Heinrich Focke, could fly at a speed of 75 miles per hour. Although mass production of military helicopters started in 1942, the license for the first certified civilian helicopter was not given until 1946.

Significant developments in helicopter engineering ensued during the first half of the 20th century, with improvements in fuels and engines. The production of lightweight turbo shaft engines in the second half of the 20th century aided in the invention of larger, faster and higher-performance helicopters. The most important apparatus in a helicopter is its rotors, which are commonly designed in the Sikorsky-layout. Many helicopters also have a smaller vertical propeller called a tail rotor mounted at the rear of the aircraft. This creates thrust in the opposite direction from the torque generated by the main rotor.

Although helicopters have the advantage of maneuverability and can take off or land vertically anywhere, a pilot can still face potential dangers like ground resonance, low-G condition, vortex ring state, etc. Therefore, it is imperative to operate within safe flight patterns and to avoid hazardous conditions.