The casing´s main purpose is to protect the camera from damage. It also provides information for shipping and selling. It also prevents sunlight from getting in.
No light gets into the shutter. This is because if the film is exposed to any light before the pictures are take then it will be destroyed. The shutter controls how long the film is exposed to light.
The lens is a curved piece of glass or plastic that redirects beams of light bouncing off ann objects to form an image.
The film is a light sensitive emulsion on a plastic base. Light reflected off the objects comes through the lens and hits the emulsion, the part of the film that allows it to record images.
The Flash Circuit
Its main purpose is to make a short flash of light when the shutter is released. This solves the problem of lack of light.
The Gas Discharge Tube
This is a tube filled with xenon gas and it has electronodes and a metal trigger plate. This is to conduct on an electrical current by moving electrons from one to the other.