A common noun is a word that refers to a person, place, or thing but is not the actual name of that particular person, place, or thing.
- It is usually written in small letters.
- Common nouns usually go with limiting modifiers such as a/an, some, every, or my.
A proper noun is a word that names a particular person, place, or thing.
- It is usually capitalized.
- A proper noun does not usually go with a limiting modifier (unless used for emphasis, such as when you refer to a person of renown, e.g. the David Attenborough).