Brake pads are steel backing plates used in disk brakes. When pressing on the rotor, they create friction. Lack of brake pads can make the whole braking system overheat and fail as the heat from the friction generated won't diffuse properly.
Bad brake pad symptoms are as follows:
You can get your brake pads replaced when you find any of the above symptoms in your car. Usually, brake pads last for about 50000 kilometers driven and need replacement after that. Replacing them on time can serve you better on the road.