What is noun in apposition?

A noun in opposition is when one noun follows another to describe it, the noun which follows is said to be in apposition to the noun which comes before it. Examples:

My brother John is home from college. (The noun John is in apposition to the noun brother.)

My neighbor, an Excellent gardener often gives me fresh vegetables.

The book, 'The Internet for Dummies', has helped be a lot.

The puppy, a poodle, was beckoning from the pet shop window.