A proper name/noun is the specific name of only
one item of a set.
The
Eiffel Tower is a proper noun;
tower is a common noun.
Mister Micawber is a proper noun;
man is a common noun.
Chicago is a proper noun;
city is a common noun.
Chevrolet is a proper noun;
automobile, sedan and
vehicle are common nouns.
Proper nouns always begin with a capital letter.