headshot vs photo

headshot and photo both are nouns.

Word	Noun	Adjective	Verb	Adverb
headshot	Yes	No	No	No
photo	Yes	No	No	No

As nouns, photo is a hypernym of headshot; that is, photo is a word with a broader meaning than headshot:

headshot: a photograph of a person's head
photo: a representation of a person or scene in the form of a print or transparent slide or in digital format

Other hypernyms of headshot include exposure, photograph, pic, picture.

headshot (noun)	photo (noun)
a shot aimed at a person's head	a representation of a person or scene in the form of a print or transparent slide or in digital format
an attempt to put the soccer ball into the net by using the head
a photograph of a person's head