Gastroesophageal reflux is a backflow (reflux or regurgitation) of food and stomach acid into the esophagus, which is the tube that connects the mouth to the stomach. When reflux irritates the lining of the esophagus and causes burning pain, difficulty eating, weight loss, or other problems, it is called gastroesophageal reflux disease (GERD).
Most babies have reflux. Babies with reflux may spit up. And some healthy babies may spit up frequently.
Babies who have GERD may cry because of the burning pain. Sometimes GERD causes breathing difficulty, if the baby breathes stomach contents into the lungs.
WebMD Medical Reference from Healthwise