Rack and pinion is a type of mechanical system used to convert rotational motion into linear motion. It consists of a round gear, called a pinion, which meshes with a linear gear, called a RACK. The pinion is attached to a rotating shaft, while the RACK is connected to a linear guide or actuator. When the pinion is rotated, it causes the RACK to move in a linear direction. This type of system is commonly used in automotive steering systems, as well as in industrial machinery and robotics.