Autogyros or gyrocopters are rotorcraft that use powered propellers to provide forward thrust, but unpowered rotors to provide lift. In 1920, Juan de la Cierva an engineer from Spain invented the autogyro. He was trying to invent a flying machine that would have a reduced risk of stalling when aircraft were at lower speeds.

Juan de la Cierva conceived a flying machine that incorporated the use of rotor blades that would rotate without the use of power. Because of the design of the rotor blades being somewhat like wings of an airplane they utilize lift and drag to effectively create un-powered rotation and lift.

This technology was eventually used as a precursor to the development of helicopters. Helicopters however use powered rotors that create lift and thrust. Helicopters also don't have fixed wings (like an airplane) unlike Juan de la Cierva's design.

Later on, Igor Benson in the 1950's would design a rotor kite or gyroglider. It had no power at all and was carried aloft by aircraft and dropped or pulled into the air by a car or boat.

Later autogyros would use Benson's design coupled with a rear mounted engine/propeller to push or provide thrust for their autogyros.

Autogyro rotors must be spinning at an appropriate speed before take off called "pre-rotation" When first developed this was achieved by using ropes and pulling it to speed somewhat like a top. Later, controlled rotor hubs that could control pitch and the use of the power-plant, transmissions and clutches to engage and disengage that would get them to the appropriate speed of rotation.

Below I have located some amazing videos of vintage autogyro testing films, some newer gyrocopters and gyrocopters with the motor in front called "tractor" configured.