main drag vs high street

main drag and high street both are nouns.

Word	Noun	Adjective	Verb	Adverb
main drag	Yes	No	No	No
high street	Yes	No	No	No

As nouns, high street is a hypernym of main drag; that is, high street is a word with a broader meaning than main drag:

main drag: the main street of a town or city
high street: street that serves as a principal thoroughfare for traffic in a town

Other hypernyms of main drag include main street.

main drag (noun)	high street (noun)
the main street of a town or city	street that serves as a principal thoroughfare for traffic in a town