low beam vs beam of light

low beam and beam of light both are nouns.

Word	Noun	Adjective	Verb	Adverb
low beam	Yes	No	No	No
beam of light	Yes	No	No	No

As nouns, beam of light is a hypernym of low beam; that is, beam of light is a word with a broader meaning than low beam:

low beam: the beam of a car's headlights that provides illumination for a short distance
beam of light: a column of light (as from a beacon)

Other hypernyms of low beam include beam, irradiation, light beam, ray, ray of light, shaft, shaft of light.

low beam (noun)	beam of light (noun)
the beam of a car's headlights that provides illumination for a short distance	a column of light (as from a beacon)