town vs Main Street

town and Main Street both are nouns.

Word	Noun	Adjective	Verb	Adverb
town	Yes	No	No	No
Main Street	Yes	No	No	No

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

town: an urban area with a fixed boundary that is smaller than a city
Main Street: any small town (or the people who inhabit it); generally used to represent parochialism and materialism (after a novel by Sinclair Lewis)

Other hyponyms of town include burg, boom town, cow town, cowtown, ghost town, hometown, market town.

town (noun)	Main Street (noun)
the people living in a municipality smaller than a city	any small town (or the people who inhabit it); generally used to represent parochialism and materialism (after a novel by Sinclair Lewis)
an urban area with a fixed boundary that is smaller than a city
an administrative division of a county