Also called: Gastroesophageal reflux disease (GERD) . Your esophagus is the tube that carries food from your mouth to your stomach. Gastroesophageal reflux disease (GERD) happens when a muscle at the end of your esophagus does not close properly. This allows stomach contents to leak back, or reflux, into the esophagus and irritate it. You may feel a burning in the chest or throat called heartburn. Sometimes, you can taste stomach fluid in the back of the mouth. This is acid indigestion. If you have these symptoms more than twice a week, you may have GERD. If not treated, it can lead to more serious health problems.