general headquarters vs HQ

general headquarters and HQ both are nouns.

Word	Noun	Adjective	Verb	Adverb
general headquarters	Yes	No	No	No
HQ	Yes	No	No	No

As nouns, HQ is a hypernym of general headquarters; that is, HQ is a word with a broader meaning than general headquarters:

general headquarters: military headquarters from which a military commander controls and organizes the forces
HQ: the military installation from which a commander performs the functions of command

Other hypernyms of general headquarters include headquarters, military headquarters.

general headquarters (noun)	HQ (noun)
military headquarters from which a military commander controls and organizes the forces	the military installation from which a commander performs the functions of command