What is a gastroscope?

A camera. It is a tiny fiber optic camera on the end of a long tube (like a thin garden hose). It is passed into the mouth, down the esophagus (food pipe) and in to the stomach. It is used by gastroenterologists to look for ailments on the lining of the intestinal tract. Often, they take biopsies through the scope, which are little scrapings on the intestinal lining so they can run additional tests.
'lit tube' & camera. A gastroscope is a modern flexible 'lit tube' with working channels (for biopsies, treatment etc.). It is used to examine the stomach and esophagus and often, the first part of the small intestine, the duodenum.