This document discusses different types of diphthongs and triphthongs. It defines diphthongs as sounds formed by combining two vowels within a single syllable, where the sound begins as one vowel and moves toward another. It describes centering diphthongs as gliding toward the schwa vowel, and closing diphthongs as ending with a glide toward a closer vowel. It also defines triphthongs as a glide from one vowel to another and then to a third, all produced rapidly without interruption.