A noun is a person, place, or thing:  apple, dog, horse.

A proper noun is specific noun, it must always be capitalized:  John, Casey, Nikki, Florida.

A common noun is a class of people, places, or things:  pets, houses, people, student.

A singular noun is one unit:  dog, table, spoon, carpet.

A plural noun is more than one unit:  dogs, tables, spoons, carpets.