Fog lights are specialized
lamps on
vehicles designed to assist seeing through
foggy conditions.
Typically, the fog will reflect light back to its source, which is why you end up blinded if you put your high-beams on in a fogbank. Car manufacturers have worked on lighting that is (typically) lower than the centerline of the car and sometimes tinted amber, which does a better job at penetrating the fog and reflecting back a less-blinding glare.
Some fog lights are original equipment manufacturer (OEM) items, while the majority are aftermarket fog light kits.