Countable nouns are nouns that can be counted.
  Example: Book, Pen, rooms, fan etc.

• We can use the indefinite article before it. 
• Example:I own a car.

• We can use the word 'many' to describe it. 
  Example:She has many friends.

• We can express its quantity by using a number before it. 
  Example: I have five apples.

• It takes on singular as well as plural forms. 
  Example:an orange / some oranges / fifty oranges

Uncountable nouns are amounts of something which we cannot count .Example: Rice, water, oil, sand etc.,

The noun is uncountable:

• A or an is not normally used in front of it. 
  Example: He is eating some rice. (NOT: He is eating a rice.)  
    Rice is treated as not countable, so some(which can be used for both countable and uncountable nouns) is used with it.

Countable and Uncountable Nouns are used with the following:

Countable Noun	Uncountable Noun
a, an, a few, several, many,	a little, much, some, plenty of,
some, plenty of, a lot of,	a lot of, a large amount of,
a large number of	a great deal of