emoticon vs facial expression

emoticon and facial expression both are nouns.

Word	Noun	Adjective	Verb	Adverb
emoticon	Yes	No	No	No
facial expression	Yes	No	No	No

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

emoticon: a representation of a facial expression (as a smile or frown) created by typing a sequence of characters in sending email
facial expression: a gesture executed with the facial muscles

Other hypernyms of emoticon include facial gesture.

emoticon (noun)	facial expression (noun)
a representation of a facial expression (as a smile or frown) created by typing a sequence of characters in sending email	the feelings expressed on a person's face
	a gesture executed with the facial muscles