Nouns fall under two classes: proper nouns; common nouns.

Proper nouns are individual names given to separate persons or things. As regards their meaning proper nouns may be personal names (Mary, Peter, Shakespeare), geographical names (New-York, London, the Caucasus), the names of the months and of the days of the week (February, Monday), names of ships, hotels, clubs, etc.

A large number of nouns now proper were originally common nouns:

Brown
Smith
Mason

Proper nouns may change their meaning and become common nouns:

George went over to the table and took a sandwich and a glass of champagne. (Aldington)

Common nouns are names that can be applied to any individual of a class of persons or things (e. g. man, dog, book), collections of similar individuals or things regarded as a single unit (e. g. peasantry, family), materials (e. g. snow, iron, cotton) or abstract notions (e. g. kindness, development).