'people' is a collective noun referring to a group of 'persons'
A 'person' is a man,woman,girl, boy ,in short any human being .
The noun refers to one's individuality as existing separate from other 'people' as a group.
'He is a nice person.'
'I don't like the people I met tonight in the party."
'people' could also refer to the group of persons belonging to a certain race or nation:
'the people of China.'