smoker vs chain-smoker

smoker and chain-smoker both are nouns.

Word	Noun	Adjective	Verb	Adverb
smoker	Yes	No	No	No
chain-smoker	Yes	No	No	No

As nouns, chain-smoker is a hyponym of smoker; that is, chain-smoker is a word with a more specific, narrower meaning than smoker:

smoker: a person who smokes tobacco
chain-smoker: a heavy smoker (usually of cigarettes) who lights one off of another

Other hyponyms of smoker include cigarette smoker, cigar smoker, pipe smoker.

smoker (noun)	chain-smoker (noun)
a passenger car for passengers who wish to smoke	a heavy smoker (usually of cigarettes) who lights one off of another
a party for men only (or one considered suitable for men only)
a person who smokes tobacco