NGB vs government agency

NGB and government agency both are nouns.

Word	Noun	Adjective	Verb	Adverb
NGB	Yes	No	No	No
government agency	Yes	No	No	No

As nouns, government agency is a hypernym of NGB; that is, government agency is a word with a broader meaning than NGB:

NGB: the agency that administers the Army National Guard and the Air National Guard; provides liaison between the Army and the Air Force and various National Guard units
government agency: an administrative unit of government

Other hypernyms of NGB include agency, authority, bureau, federal agency, office.

NGB (noun)	government agency (noun)
the agency that administers the Army National Guard and the Air National Guard; provides liaison between the Army and the Air Force and various National Guard units	an administrative unit of government