Basicalyl, "People" is used to refer to a collective group of individuals. (The people of New York are very busy.) "Person" is used to identify an individual. (He is a very busy person.) There are other uses, but this is the most common .
okay, thanks, Gideon, it's v easier to understand the two words.@Gideon
Person - Singular. How many people? One person. People - Plural / many ( ordinarily used/less formal). My people are here.
Persons - Plural / many ( mostly used for formal/official purposes). An undisclosed number of persons ....