How to use Articles

Articles are A,  An and The.
The simplest key to use a and an is that a is used before nouns beginning with consonants .
eg.  Sam is reading a book.

an is used before nouns beginning  from vowels.
eg.  I am eating an orange.

Please note-
1. Some vowels have a consonant sound.  In cases like these a is used with nouns.
eg.  I've been to  a European  city many times.
2. Some words begin with H that we donot hear while saying the word.  In these cases,  an is used before  nouns .
eg.  I have been waiting for an hour. 

The is used before a noun when we are talking to someone who already understand which person or thing we mean. Intrestingly, use of a and the confuse people.  Let us understand this concept with examples .
Have you saved the money that i gave you?
My mother is working in the kitchen.

The simple examples above will help you understand the use of a, an and the.