man vs human beings

man and human beings both are nouns.

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

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

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

As nouns, human beings is a hyponym of man; that is, human beings is a word with a more specific, narrower meaning than man:

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

man (noun)	human beings (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

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