human beings vs man

human beings and man both are nouns.

Word	Noun	Adjective	Verb	Adverb
human beings	Yes	No	No	No
man	Yes	No	Yes	No

As nouns, human beings and man are synonyms defined as:

Other synonyms of human beings include human race, humanity, humankind, humans, mankind, world.

As nouns, man is a hypernym of human beings; that is, man is a word with a broader meaning than human beings:

human beings: all of the living human inhabitants of the earth
man: any living or extinct member of the family Hominidae characterized by superior intelligence, articulate speech, and erect carriage

Other hypernyms of human beings include group, grouping, homo, human, human being.

human beings (noun)	man (noun)
all of the living human inhabitants of the earth	all of the living human inhabitants of the earth
	any living or extinct member of the family Hominidae characterized by superior intelligence, articulate speech, and erect carriage
	game equipment consisting of an object used in playing certain board games
	an adult person who is male (as opposed to a woman)
	someone who serves in the armed forces; a member of a military force
	the generic use of the word to refer to any human being
	a manservant who acts as a personal attendant to his employer
	an adult male person who has a manly character (virile and courageous competent)
	a male person who plays a significant role (husband or lover or boyfriend) in the life of a particular woman
	a male subordinate

human beings (verb)	man (verb)
	provide with workers
	take charge of a certain job; occupy a certain work place