explorer vs navigator

explorer and navigator both are nouns.

Word	Noun	Adjective	Verb	Adverb
explorer	Yes	No	No	No
navigator	Yes	No	No	No

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

explorer: someone who travels into little known regions (especially for some scientific purpose)
navigator: in earlier times, a person who explored by ship

explorer (noun)	navigator (noun)
someone who travels into little known regions (especially for some scientific purpose)	in earlier times, a person who explored by ship
	the member of an aircrew who is responsible for the aircraft's course
	the ship's officer in charge of navigation