Some cars like Alto,Belta,Vitz etc have only a singly bulb in their headlight.
In these types of cars, the bulb contains two filaments, one for low beam and one for high beam.
Other cars like Civic,Corolla have two separate bulbs for each beam totalling four bulbs.Each of the four bulbs contain only one single filament.
The high beam filament burns at a higher wattage hence it is brighter and the low beam burns at a low wattage.
If you take an H4 bulb and look at its base, you will see something like 55W/60W ... now this tells you that the low beam consumes 55Watts and the High beam consumes 60Watts.
I hope I clearified everything.
