A noun is a word or set of words for a person, place, thing, or idea. A noun of more than one word (tennis court, gas station) is called a compound noun.
There are common nouns and proper nouns. Common nouns are words for a general class of people, places, things, and ideas (man, city, award, honesty). They are not capitalized. Proper nouns are always capitalized. They name specific people, places, and things.