and ‘An’ are indefinite articles. They are used to refer things which we do not
know specifically. They are the same for all genders.
example: a girl, an apple, an umbrella etc.
is used before a word that begins with a consonant sound. All other letters of
alphabet excluding vowels are called consonants. Example: a bag, a cat,
a drum etc.
is used before a word that begins with a vowel sound. Letters a, e, i, o, u of
the alphabet are called vowels. Example: an apple, an orange etc.