1.- COUNTABLE NOUNS:

It's very easy to recognize countable nouns. They are things that we can count. Take for example, the word "book". We can count books. We can have one, two, three or more books. Countable nouns can be singular or plural:
Example 1: My child is playing in the garden
Example 2: Her paintings are very expensive

We can use the indefinite article a/an with singular countable nouns: Example: A dog is an animal.
As you can see, "a" is used before a consonant "a dog", and "an" is used before a vowel "an animal"
When a countable noun is plural, it can be used alone (Example: I like apples ) or with one of the following quantifiers:
a) SOME (Affirmative sentences) ANY (Negative and Interrogative sentences):

Examples: I have got some coins. There aren't any clothes

b) A LOT OF (Affirmative sentences), MANY (Negative and Interrogative sentences):

Examples: There are a lot of books here We don't have many friends

c) FEW (Negative meaning), A FEW (Positive meaning):

Examples: He's not very sociable, so he's got few friends I've got a few sweets for you