• Heartburn is an unpleasant feeling of burning within the chest area caused by acid in the esophagus. Heartburn at night is called nighttime heartburn.

• GERD, or gastroesophageal reflux disease, refers to the clinical manifestations of reflux of stomach contents into the esophagus.

• Erosive GERD is gastroesophageal reflux disease with erosions in the esophagus. Erosions are shallow sores in the lining of the esophagus.

• Nighttime GERD is gastroesophageal reflux disease with symptoms occurring at night.