Auto transmission choices refer to the different types of gear systems available in vehicles. Common choices include manual, automatic, semi-automatic, and continuously variable transmissions. Manual transmissions require the driver to shift gears manually, while automatic transmissions shift gears automatically. Semi-automatic transmissions are a combination of manual and automatic transmissions, and continuously variable transmissions use a belt and pulley system to provide an infinite number of gear ratios. The term 'gears' is often used to refer to these auto transmission choices.