If one of the front headlights goes bad you will need to find replacement headlights as soon as possible because it is illegal to drive a vehicle at night either without headlights or with only one headlight. When you do find those replacement parts you need to make sure the aftermarket or factory replacement parts are DOT approved especially if you are going to replace those headlights with an aftermarket light assembly that is not the stock part for you make and model vehicle.
The Right Headlight
Yes, headlights come in both right and left assemblies for most vehicles. In some vehicles that headlight assembly will be a composite headlight which is a headlight that is made up of individual components so that in different scenarios you can replace just one part of the entire headlight and not have to find replacement headlights for the entire unit. Of course if the entire unit is damaged in an accident it will have to be replaced. The other type of assembly is called a sealed headlight which means that all of the parts of the headlight which includes the reflectors, lens, and bulb filament are contained in a tightly sealed unit that is all one piece. If your vehicle has one of the sealed headlight assemblies they you will be looking at auto accessories websites for one of these sealed units.
When your lights fail to work it can mean that the light bulb has burned out and thus the entire unit has failed in a sealed unit or a bulb in a composite unit. But there may be another issue if it is not the assembly but the wiring attaching the headlight assembly to the vehicle. In this case you would have to take the headlight assembly out and check the wiring.