The Camera is a stationary installations in Barotrauma. It allows you to look outside the submarine.
The Camera is useful for seeing potential targets or generally observing the outside of the submarine.
The Periscope is where a crewmember operates the Camera. In the submarine editor, the Periscope must be wired to the Camera where the Camera's control_in pin. Only one crewmember can operate a Periscope at a time. The connected Camera is aimed using a crosshair that replaces the mouse when interacting with the Periscope.