On a car, "dual" refers to the air conditioning zone control button.

Here are some related information about "dual":

1. "Dual" is used to adjust and regulate the temperature, humidity, air cleanliness, and air flow in a car to create a comfortable and healthy environment for passengers. It can also improve the driving experience for the driver.

2. When you press the "dual" button, you can adjust the temperature of the driver or passenger seat independently, allowing for different temperature settings for each zone. This ensures that each passenger can have their own preferred temperature.