Heartburn is a symptom synonymous with gastroesophageal reflux disease (GERD), but as our knowledge advances, we find that GERD is a more complex disorder than was originally thought. First, it is known that almost two-thirds of those with typical heartburn do not have erosions and this condition—nonerosive reflux disease (NERD)—is a heterogenous disorder. With the advent of pH impedance testing, it is further recognized that NERD consists of 3 phenotypes, namely, true NERD, hypersensitive esophagus (with Rome IV, it is now termed reflux hypersensitivity) and functional heartburn (Figure 1).