There are 6 main parts to the Nikon camera: Casing, Shutter, Lens, Film, Flash Circuit and the Gas Discharge Tube. Each part his it's own job, and together they work as a system to take and create a photo.
Going from the outside to the inside, the casing plays a large part in protecting the film from stray beams of light. If some of that light snuck through and touched the film, it would be unable to take another picture correctly. The casing also protects the fragile interior parts of the camera if dropped.
The shutter is one of the main moving parts in the camera. When taking a picture, the shutter opens for a certain amount of time exposing select amount of light. If there was no shutter the film would be constantly exposed to light making it ineligible to take and produce pictures.
Although it may seem small, the lens plays a large part in recording a photo. The lens redirects, slows, and bends light waves to recapture the actual scene. It deals with each color of light in different ways as the are different waves.
The film is a light sensitive emulsion, meaning it changes when it comes in contact with light. When the shutter opens it allows a select amount of light through that touches the film after being redirected by the lens. As soon as the light touches the film it records the image. If to much light touches it however, it will not be able to take another photo as it is rendered useless.
The Flash Circuit
This electronic circuit is responsible for directing the energy for the flash. The flash is needed in some situations for the perfect amount of lighting when the area where you are taking a picture lacks the required light. This distributed light will then touch the film preserving a close to perfect image of the scene.
The Gas Discharge Tube
This tube is filled with xenon gas (the gas in neon colors). This gas moves the electrical particles in certain directions. Only a few thousand volts is required to make the gas conductive and redirect it around the flash circuit.