What distinguishes a proper noun from a common noun?

Answer 1

A proper noun is a name of something specific (like a persons name). A common noun is a name that describes a group (such as man, horse, etc)

Answer 2

A proper noun is the specific name of a person, place, or thing and is always capitalized, while a common noun refers to a general person, place, or thing and is not capitalized unless it is at the beginning of a sentence. Examples of proper nouns include "Mary," "Paris," and "Coca-Cola," while examples of common nouns include "girl," "city," and "soda."