"Manual" mode in the context of a Mercedes car refers to "手动" or "手动驾驶" mode. When you select this mode, you are telling the vehicle that you want to control the acceleration and braking with the gear shift lever (or paddles on some models) instead of letting the car do it automatically. This is also called "M" mode. In manual mode, the driver must use the clutch and gear shift to control the speed of the car.This mode is useful when driving on rough terrain or when you want to save fuel.