Heartburn, a burning pain in your chest, actually has nothing to do with your heart. Rather, the name simply describes the location of the pain. When you experience heartburn, it means the acid in your stomach has backed up into your esophagus, the tube that connects your mouth to your stomach.
When you swallow, the valve in your stomach entrance, called the lower esophageal sphincter (LES), relaxes just enough to allow the food or drink into your stomach and then close. This also keeps your stomach acid in your stomach. Heartburn results from a process called acid reflux, where the LES doesn’t fully close, leaving an opening for the acid to travel up your esophagus, often along with regurgitated food.