汽车 (qìchē) is the standard word for 'car, automobile' — a four-wheeled motor vehicle for personal transport. It's more specific than 车 (chē), which can mean any vehicle (bike, bus, truck). 车辆 (chēliàng) is a formal, collective term for 'vehicles', and 轿车 (jiàochē) refers specifically to a sedan car.