noun vs. proper noun

any member of a class of words that can function as the main or only elements of subjects of verbs (A dog just barked), or of objects of verbs or prepositions (to send money fromhome ), and that in English can take plural forms and possessive endings (Three of his buddies want to borrow John's laptop). Nouns are often described as referring to persons, places, things, states, or qualities, and the word noun is itself often used as an attributive modifier, as in

Grammar.,  a noun that is used to denote a particular person, place, or thing, as Lincoln, Sarah, Pittsburgh, and Carnegie Hall.