foreigner vs traveller

foreigner and traveller both are nouns.

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

As nouns, traveller is a hypernym of foreigner; that is, traveller is a word with a broader meaning than foreigner:

foreigner: a person who comes from a foreign country; someone who does not owe allegiance to your country
traveller: a person who changes location

Other hypernyms of foreigner include traveler.

foreigner (noun)	traveller (noun)
a person who comes from a foreign country; someone who does not owe allegiance to your country	a person who changes location
someone who is excluded from or is not a member of a group