A hernia is an abnormal hole or weakness in the abdominal wall that allows internal organs or tissues to protrude outside of the body. The most common types are inguinal hernias, which occur in the groin area, and hiatal hernias, which involve part of the stomach protruding into the chest. Hernias can range from harmless to a medical emergency if the blood supply is cut off. Treatment involves surgery to repair the abdominal wall, though some small reducible hernias may only require monitoring.