A video gastroscope is a thin, flexible tube with a tiny camera at its tip, used by doctors to visually examine the esophagus, stomach, and duodenum (upper GI tract) by sending images to a video screen, allowing for diagnosis of issues like ulcers or inflammation, and even therapeutic actions like taking biopsies or removing polyps. Key features include high-definition imaging (HDTV), illumination, channels for air/water/suction, and control knobs for tip articulation, providing detailed, real-time views for both diagnostic and treatment procedures.