If this light is on, you are running out of gas or there is a problem with the fuel level sensor.
You can drive to a nearby gas station to refill the tank. Have your car checked by an auto mechanic if there is gas in the car and the light stays on.
Usual problems: out of gas, fuel level sensor malfunction, bad electrical connection
A fault that opens the electrical circuit causes the indicator to show the tank as being empty, which signals the driver to refill the tank. If the low fuel light remains on and you have gas in the tank, there is an electrical problem.