Heartburn occurs when acid from the stomach moves back into the esophagus, thus causing pain and discomfort in your chest and maybe even a bitter taste in your mouth.
The fluids produced by your stomach to help your body digest food contain a powerful acid called hydrochloric acid — something your stomach is naturally protected from, but your esophagus is less so. Therefore, if the hydrochloric acid moves back or “refluxes” into your esophagus, the more sensitive lining of the esophagus can become irritated, thus resulting in heartburn pain.
And if you have heartburn symptoms occurring two or more days a week, that’s classified as frequent heartburn. So it’s the same discomfort of heartburn, just more frequent.