Endoscopy is a diagnostic procedure used to examine the GI tract, allowing doctors to diagnose and treat conditions affecting the colon, intestines, and stomach by inserting a flexible tube called an endoscope. It is recommended for symptoms such as unexplained abdominal pain, blood in stool, chronic heartburn, and in cases with a family history of colon cancer. While generally safe, the procedure carries some risks, and patients should seek an experienced doctor for optimal care.