DETERMINERS

Definition

Determiners are small words that come before nouns. Determiners give information about the noun. Articles - the / a /  an - are one type of determiner.

Example

   A tree is burning

   The tree in front of the house is burning

Explanation

Articles

• are either indefinite (a/an), definite (the), or zero (nothing).
• come before a noun, and before an adjective + noun (a tree, a tall tree).
• are not used before names of people or places.

Indefinite articles (a / an) --

• are used when the nouns are not specific. For example: "A tree is burning." We do not know which tree because it is general, not specific.
• are used with singular count nouns. For example: "a cat, an apple."
• have two forms: a and an. "A" is used when the first sound of the noun is not a vowel. For example: "a cow, a computer, a book". "An" is used when the first sound of the noun is a vowel (a, e, i, o, u ) sound. For example: "an apple, an orange, an animal". But note that it is "a university" because the first sound is y, even though the first letter is u.

Definite article (the) --

• is used when the nouns are specific. For example: "The tree in front of the house is burning." We know which tree (the tree in front of the house). It is specific.
• is used with singular and plural count nouns. For example: "the cat, the apples".
• is used with non-count nouns. For example: "the money".

Zero article --

• is used when the nouns are not specific. For example: "I like dogs."
• is used with plural count nouns. For example: "Apples taste good."
• is used with non-count nouns. For example: "Money is important."

Source :
http://grammar.ccc.commnet.edu/grammar/determiners/determiners.htm
https://www.google.com/?gws_rd=ssl#q=determiner+of+article
http://web2.uvcs.uvic.ca/elc/sample/beginner/gs/gs_32.htm