Heartburn is the inflammation of the esophagus. It is also known as pyrosis. The major cause of heartburn is reflux. This is when the esophagus bottom edges are not tightly shut, and acid moves form the stomach up into the esophagus. Hiatus Hernia's also cause heartburn. This also occurs when the ends of the esophagus are not shut, and the stomach lining moves up the esophagus. There are many other causes of heartburn, some of which being: obesity, drinking hot or cold beverages, extensive alcohol usage, smoking, foods (acidic), certain ....