This document discusses peptic ulcers, including their definition, locations, causes, and characteristics. A peptic ulcer is an erosion of the GI mucosa caused by stomach acid and pepsin. The main sites are the stomach (gastric ulcer) and duodenum (duodenal ulcer). Acute ulcers are usually caused by NSAIDs, stress, sepsis, burns, or head injuries. Chronic ulcers have multiple potential causes, including H. pylori infection, acid hypersecretion, smoking, diet, genetics, and decreased mucosal resistance. Complications can include bleeding, perforation, and malignant transformation. Treatment involves acid-reducing drugs, eradicating H. pylori,