Heartburn is a fiery sensation that often begins behind the breastbone and moves upward to the throat. Described as a burning feeling in the chest, it's often accompanied by a sour taste in the mouth or a sensation of food coming back into the mouth. Some liken it to a feeling of pressure or discomfort in the chest. What does heartburn feel like? While occasional heartburn is common and usually harmless, persistent symptoms may indicate gastroesophageal reflux disease (GERD) and should be addressed by a healthcare professional.