"Peoples" is the plural of "people." It refers to different groups of people within a geographic region, in order to differentiate them based on culture and/or ethnicity. (Example: the native peoples of Canada) One person. Two people.

So, technically, peoples is the plural of the word people, making it a type of plural on a plural. Don’t worry too much about the details. The key to getting it correct is understanding whether you are using the possessive of the word people or the word peoples — we’ll see how that works, next.