spelunker vs explorer

spelunker and explorer both are nouns.

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

As nouns, explorer is a hypernym of spelunker; that is, explorer is a word with a broader meaning than spelunker:

spelunker: a person who explores caves
explorer: someone who travels into little known regions (especially for some scientific purpose)

Other hypernyms of spelunker include adventurer.

spelunker (noun)	explorer (noun)
a person who explores caves	someone who travels into little known regions (especially for some scientific purpose)