auto vs motor vehicle

auto and motor vehicle both are nouns.

Word	Noun	Adjective	Verb	Adverb
auto	Yes	No	No	No
motor vehicle	Yes	No	No	No

As nouns, motor vehicle is a hypernym of auto; that is, motor vehicle is a word with a broader meaning than auto:

auto: a motor vehicle with four wheels; usually propelled by an internal combustion engine
motor vehicle: a self-propelled wheeled vehicle that does not run on rails

Other hypernyms of auto include automotive vehicle.

auto (noun)	motor vehicle (noun)
a motor vehicle with four wheels; usually propelled by an internal combustion engine	a self-propelled wheeled vehicle that does not run on rails