Heartburn is a common problem created by acid reflux, a condition where some of the stomach contents are forced back up into the esophagus. It creates a burning pain in the lower chest.
Persistent acid reflux that happens more than twice a week is referred to as gastroesophageal reflux disease, or simply GERD. Heartburn is felt when stomach acid flows back up into the esophagus, the pipe that carries food from the mouth to the stomach. Furthermore, heartburn is a symptom of GERD.