Heartburn is a burning sensation in your chest, just behind your breastbone. Technically called gastroesophageal reflux disease (GERD), heartburn occurs when stomach contents back up into your esophagus. Sour taste and the sensation of food coming back into your mouth may accompany the sensation.
Heartburn usually happens after you've eaten a meal, and it may occur at night. The pain usually worsens when you're lying down or bending over.