Simplify the following text for a Grade 6 native English-speaking person.
Original: Technically , a diphthong is a vowel with two different targets : That is , the tongue moves during the pronunciation of the vowel .
Simplified: A Diphthong ( pronounced `` DIF-thong '' ) is a vowel that a person has to move his or her mouth into two different positions to make . It is a vowel where two different vowel qualities can be heard .