A common noun names a person, place, or thing. A common noun begins with a lowercase letter. It is a general word for a group of people, things, or places.
I think inventors are really creative people.
Louis can't decide which new city he wants to visit on his next vacation.
What month were you born in?
A proper noun names a particular or specific person, place or thing.
Each important word of a proper noun begins with a capital letter.
Wilbur and Orville Wright invented and built the first flying airplane in the early 1900's.
Louis is going to visit Rio for his next vacation.
I was born in October, when the leaves start to change color and fall.