retreated vs people

retreated and people both are nouns.

Word	Noun	Adjective	Verb	Adverb
retreated	Yes	No	No	No
people	Yes	No	Yes	No

As nouns, people is a hypernym of retreated; that is, people is a word with a broader meaning than retreated:

retreated: people who have retreated
people: (plural) any group of human beings (men or women or children) collectively

retreated (noun)	people (noun)
people who have retreated	(plural) any group of human beings (men or women or children) collectively
	the body of citizens of a state or country
	members of a family line
	the common people generally

retreated (verb)	people (verb)
	fill with people
	furnish with people