How do I know the difference between an and a?

'A' and 'an' are both indefinite articles used before nouns or before adjectives that modify nouns. To determine if you should use 'a' or 'an' before a word, you need to listen to the sound the word begins with. Use 'a' if the word begins with a consonant sound and use 'an' if the word begins with a vowel sound.

Explanation:

i think it is called the president's cabinet.