The disposable camera case protects and holds the internal parts in place, blocks any sunlight from reaching the film.
The shutter opens and closes at a fast rate to let a certain amount of light in of the scene you are capturing, which takes the picture.
The lens is a plastic or glass dome-shaped piece that takes light beams of the scene being captured for the picture and focuses them onto the film when the shutter opens.
The film is a long piece of light sensitive emulsion on a plastic base that gets exposed to the light beams of the scene when the shutter opens. When the light hits the film, the film gets the light beams imprinted on it, and a picture is made.
The Film Circuit
The flash circuit is a device used in both disposable and normal cameras to light up a dark environment for the small amount of time that the shutter opens so that the film is exposed to enough reflected beams of light to capture the scene.
The Gas Discharge Tube
The Gas Discharge Tube is a small tube inside the flash that contains xenon. When the button to take a picture is pressed, electricity is introduced through diodes on either side of the tube, which comes into contact with the xenon and excites the particles. This causes a reaction to happen with the xenon, which cause a bright flash of light to happen.