The **front fog lights** are a type of lighting on vehicles used to improve visibility in adverse conditions such as fog, snow, heavy rain, and smoke. These lights can be white or yellow.

- **Optionality:** Front fog lights are **optional** on vehicles. This means that it is not mandatory for all vehicles to have them installed. Unlike other lights, such as high beams, which are mandatory for all cars, front fog lights are installed according to the preference of the manufacturer or the vehicle owner.

- **Proper use:** It is recommended to use front fog lights together with the position lights. They can also be used simultaneously with high and low beams to improve visibility in adverse weather conditions.

In summary, although front fog lights are useful in certain situations, their installation is not a mandatory requirement for all vehicles, which makes them **optional**.