smile vs facial gesture

smile and facial gesture both are nouns.

Word	Noun	Adjective	Verb	Adverb
smile	Yes	No	Yes	No
facial gesture	Yes	No	No	No

As nouns, facial gesture is a hypernym of smile; that is, facial gesture is a word with a broader meaning than smile:

smile: a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement
facial gesture: a gesture executed with the facial muscles

Other hypernyms of smile include facial expression.

smile (noun)	facial gesture (noun)
a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement	a gesture executed with the facial muscles

smile (verb)	facial gesture (verb)
change one's facial expression by spreading the lips, often to signal pleasure
express with a smile