A noun is the name of a person, place or thing. There are different kinds of nouns.
1.    Proper noun
2.    Common noun
3.    Collective noun
4.    Abstract noun

Proper noun

Look at the following sentence: Solomon was a wise king.

Here the noun Solomon is the name of a particular king, but the noun king may be applied to any other king as well as Solomon. A noun which is used as the name of a particular person, place or thing is called a proper noun. Examples are: John, Alice, Krishna, Mumbai, France, Amazon, Google etc.

Proper nouns always begin with a capital letter.

• I live in Mumbai. (NOT I live in mumbai.)
• Paris is the capital of France.

Proper nouns cannot be used with articles.

• Alice is a doctor. (NOT The Alice is a doctor.)
• Helen of Troy was known for her beauty. (NOT The Helen was known for her beauty.)

Common noun

A common noun is a name given in common to every person or thing of the same class or kind. Examples are: girl, boy, man, woman, student, country, river, star, poet, writer, painter etc.

• Shakespeare was a great playwright. (Shakespeare – proper, playwright – common)
• Picasso was a great painter. (Picasso – proper, painter – common)

Note that common nouns include what are called collective nouns and abstract nouns.

Related posts:

1. Parts of Speech I