Acidity or heartburn simply indicates an increased level of acids in the stomach. Our stomach secrets Hydrochloric Acid, which is responsible for breaking down the food particles to the smallest forms in order to facilitate digestion. The secretion is initiated by the food intake. Due to some abnormality or other, sometimes there is more secretion of gastric acid (Hydrochloric Acid), which travels up through the esophagus and offers a heartburn and sour mouth like sensation. This is known as hyperacidity or simply acidity in humans.