This document summarizes information about gastroenteritis or diarrhea. It begins with an introduction and table of contents. It then discusses diarrhea in three chapters: advance, study, and conclusion. The advance chapter defines the background, problems, and objectives of the document. The study chapter defines diarrhea, discusses etiology including infection, malabsorption, diet, and psychological factors. It also covers pathogenesis, complications like dehydration, and prevention and treatment methods. The conclusion chapter restates the definition of diarrhea, summarizes the four causes and mechanisms, complications, prevention methods, and treatment approach of rehydration. The document aims to educate about diarrhea for college students and readers.