selectman vs elected official

selectman and elected official both are nouns.

Word	Noun	Adjective	Verb	Adverb
selectman	Yes	No	No	No
elected official	Yes	No	No	No

As nouns, elected official is a hypernym of selectman; that is, elected official is a word with a broader meaning than selectman:

selectman: a male elected member of a board of officials who run New England towns
elected official: official who won the office in a free election

Other hypernyms of selectman include adult male, man.

selectman (noun)	elected official (noun)
a male elected member of a board of officials who run New England towns	official who won the office in a free election