Hi! There is no difference between a and an. The only thing you have to worry about is the word just after. If the word start with a consonant you put "a". If it start with a vowel, you put "an". Examples: "A car", "An apple" "Car" start with a consonant "C" so I put "a". And "Apple" start with a vowel "a" so I put "an"

We use "a" before nouns which begin with consonant sound. For example: a boy, a girl... We use "an" before nouns which begin with vowel sound. Example: an apple, an hour. Good luck.

easy article i hope you serve example I'm an engineer i'm a doctor