The document discusses the transmission system of an automobile. It describes the purpose of a transmission as sending power from the engine to the drive wheels. It then discusses the main types of transmissions, focusing on continuously variable transmissions (CVTs). CVTs allow for infinite gear ratios between the engine and wheels for better acceleration and fuel efficiency. The document outlines the key components of a transmission system, including the flywheel, clutch, gearbox, propeller shaft, differential, axles and gears. It provides details on specific parts like the purpose of a differential and how gear ratios are calculated.