Acid reflux is a condition which occurs stomach acids and the other stomach contents happen to back up into the esophagus through the LES (Lower esophageal sphincter). Lower esophageal sphincter is a kind of muscular ring which is located on digestive tract esophagus meets the upper part of the stomach. The lower esophageal sphincter opens to allow food to flow into the stomach when swallowing. It is normally closed to prevent the stomach contents from rising into the upper part of the esophagus. So, you need to know about acid reflux symptoms.