Three point linkage (or three-point-hitch) is a standardised system to attach implements to tractors. They comprise of three movable arms assembled in a triangle or 'A' formation, and are controlled by the hydraulic system allowing lifting, lowering and tilting.
The three-point hitch is now standard equipment on almost all tractors, but back in 1926, when patented in Great Britain by an Irish engineer named Harry Ferguson, it revolutionized the way implements were attached to tractors.