An ulcer is a sore that develops on the lining of the stomach, small intestine, or other parts of the body. The most common type is a peptic ulcer, which can be caused by factors such as Helicobacter pylori infection, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), or excessive alcohol consumption. Symptoms may include abdominal pain, bloating, and indigestion. Ulcers can lead to serious complications if left untreated, such as bleeding or perforation of the digestive tract. Treatment often involves medications to reduce stomach acid, antibiotics to eliminate infections, and lifestyle changes to promote healing.