Proper nouns are different from common nouns in several ways.
First of all, proper nouns are always capitalized. Common nouns are never capitalized.
Secondly, proper nouns are specific names for some persons, places, and things.
Thirdly, proper nouns are never ideas – only persons, places, and things.
Here are some proper nouns that name actual people:
Mom
Dad
Bobby
President Lincoln
Mr. Potato Head
Dr. Martin Luther King
Here are proper nouns that name actual places:
Washington School
Target
The U.S. Capitol
Largo, Florida
Paris, France
Yellowstone National Park
Sometimes proper nouns name things that are special and unique:
The U.S. Constitution
The Chicago Tribune
The Declaration of Independence
Valentines Day
Dad’s Root Beer
September
Friday
Always capitalize proper nouns that are names for actual people, actual places, and actual things.