What are endoscopes?

According to the U.S. Department of Veterans Affair an endoscope

Endoscopes are miniature, elongated microscopes that physicians use to perform minimally invasive procedures on patients - in their hollow organs or internal canals.  Endoscopes may be rigid or flexible.  Both are delicate, precision instruments.  Most flexible endoscopes contain systems to deliver light, suction, air and water.  Another internal system makes it possible for the physician to control bending of the instrument, referred to as distal-end angulation.  Flexible endoscopes contain either an electronic video camera chip or glass fibers to produce or “return” images for the physician to view.  Rigid endoscopes deliver light through thin stainless-steel tubes and “return” images through glass lenses.