Omeprazole 20mg is a type of medicine known as proton pump inhibitors. This medication targets symptoms of acid reflux, providing relief from indigestion and heartburn. Taken orally, Omeprazole tablets prevent proton pumps from working properly, reducing the amount of stomach acid in your stomach, helping prevent and treat stomach ulcers.  Omeprazole is used to treat certain conditions where there is too much acid in the stomach. It is used to treat gastric and duodenal ulcers, erosive esophagitis, and gastroesophageal reflux disease (GERD). GERD is a condition where the acid in the stomach washes back up into the esophagus.