Peptic ulcers are sores that form on the lining of your esophagus, stomach, or duodenum. Your esophagus is the tube that carries food from your mouth down to your stomach. The duodenum is the upper part of your small intestine.  Peptic ulcers that form on the lining of your esophagus are called esophageal ulcers.  Ulcers that form on the lining of your stomach are called gastric ulcers.  And ulcers that form on the lining of your duodenum are called duodenal ulcers.  The two most common types of peptic ulcers are gastric and duodenal ulcers.