The terms acid reflux, heartburn, and GERD are often used interchangeably, but there is a difference among these three digestive disorders:
Acid reflux is the reason you have heartburn. It is the underlying condition that allows stomach acid to escape into the esophagus. Reflux is the result of a malfunctioning lower esophageal sphincter (LES). The LES is a group of muscles that allows food and fluid to pass into the stomach and block any of the stomach contents from getting into the esophagus.
Acid reflux is not necessarily a chronic condition. Any time your LES malfunctions, you're experiencing reflux. So, even if you get reflux only once a year, you're still considered to have acid reflux.
Heartburn is a symptom and not a disease or condition. Heartburn is one of the most common symptoms of acid reflux and gastroesophageal reflux disease (GERD). It's a burning sensation in the chest that results from the esophagus being exposed to stomach acid.
GERD is a chronic condition. Most doctors will diagnose you with GERD if you experience heartburn or other reflux symptoms two or more times a week. Acid reflux may not require treatment, but GERD usually will.