The casing protects the parts inside, holds the parts in place, and keeps light from coming in contact with the film.
The shutter controls when and for how long the film is exposed to the light by opening when you want to take a picture.
The lens redirects the beams of light bouncing off the object you want to take a picture of so that they come together to form an image.
The film takes light reflected off objects in the camera's field of view and the light strikes an emulsion on the film to create a picture.
The flash circuit is used to make lots of extra light so a picture can be put on film. The flash lights up a up the room for a second so light refection is more powerful to make a clearer picture on the film.
Gas Discharge Tube
The gas discharge tube is filled with xenon gas that moves a electrical current by moving electrons from one electrode to the other using a few thousand volts of electricity.