foreigner vs gringo

foreigner and gringo both are nouns.

Word	Noun	Adjective	Verb	Adverb
foreigner	Yes	No	No	No
gringo	Yes	No	No	No

As nouns, gringo is a hyponym of foreigner; that is, gringo is a word with a more specific, narrower meaning than foreigner:

foreigner: a person who comes from a foreign country; someone who does not owe allegiance to your country
gringo: a Latin American (disparaging) term for foreigners (especially Americans and Englishmen)

Other hyponyms of foreigner include au pair, deportee, exile, import, importee, metic.

foreigner (noun)	gringo (noun)
a person who comes from a foreign country; someone who does not owe allegiance to your country	a Latin American (disparaging) term for foreigners (especially Americans and Englishmen)
someone who is excluded from or is not a member of a group