hub vs down town

hub and down town both are nouns.

Word	Noun	Adjective	Verb	Adverb
hub	Yes	No	No	No
down town	Yes	No	No	No

As nouns, down town is a hyponym of hub; that is, down town is a word with a more specific, narrower meaning than hub:

hub: a center of activity or interest or commerce or transportation; a focal point around which events revolve
down town: the center of a city

Other hyponyms of hub include civic center, municipal center.

hub (noun)	down town (noun)
the central part of a car wheel (or fan or propeller etc) through which the shaft or axle passes	the center of a city
a center of activity or interest or commerce or transportation; a focal point around which events revolve