Articles are words that define a noun as specific or unspecific.  
  Indefinite articles 'a' and 'an' are placed before singular countable nouns. We do not put 'a' or 'an' before a plural noun because 'a' or 'an' means one.  

'A' is placed before a noun that begins with a consonant and the 'u' sound.

For example:

- A lion

- A book

- A temple

- A university

- A European man


'An' is placed before a noun that begins with a vowel and before the silent 'h'.

For example:

- An ant

- An umbrella

- An apple

- An honest lady

- An hour


'The' is a definite article. We use it to refer to:

a. A specific thing / person.

For example:

- The dog that bit me ran away.

- Mom, you left the iron switched on.


b. Something already mentioned earlier.

For example:

- Yariz is a car produce by a company named Toyota. The car is well known to be small, good fuel consumption and convenient to drive around town.


c. A thing that is the only one its kind.

For example:

- The moon

- The Sun


d. When the noun is definite or certain, this means that the information is true or known.

For example:

The winter of 1947 was one of the coldest in Britain.

- I looked it up on the Internet.