Nouns

Nouns are a part of speech typically denoting a person,place,thing,animal,ideas or concepts.
Following are some of the examples :

I went to the city.
I went to India.

We can observe that in the first sentence the noun is not capitalized while in the second it is.
In addition of being a  person,place,thing,animal or concepts,Nouns can be common and proper.Common nouns are not capitalized while Proper nous are capitalized.

Some of the examples of common nouns:

1. He bought a new car on his birthday.
2. I am living in tirupathi.
3. Give me a call  when you arrive.

Some of the examples of proper nouns:

1. I live in India.
2. To Kill A Mockingbird is my favorite book.
3. The Pacific Ocean is the world's biggest ocean.