The USB port of your vehicle can accomplish more than you realize; these buttons may also fulfill various functions depending on your car’s make, model, and year.
You might notice an auto-dimming button instead of a manual control on your rear-view mirror. Usually, you will press it to switch it off or on, accompanied by a light indicator to inform you when it is active. When engaged, it automatically modifies your rear-view mirror based on headlight glare from behind the vehicle. This facilitates better visibility and allows you to maintain a grip on the wheel for safer driving.
Nonetheless, some vehicles have one or several additional buttons that activate various features. This can vary greatly depending on your specific vehicle, as they are not as standardized as dimming the rear-view mirror. Features can include connecting to a home system, calling for assistance in emergencies, and more.