The lens also effects how large the image appears based on the focal length of the lens. The aperture is located in the lens and is a set of leaf like piece of metal that can change the size of the hole that lets in light. Finally, we have the film holder inside the camera. This must have some attachment that allows for the film to be moved which can either be a lever or a motor. Shutter Controls how LONG light enters the camera.
B stands for bulb and holds the shutter open as long as the shutter release is held down.
This used to be attached to a long hose to a bulb held in the photographers hand, thus the name Bulb. Each shutter speed lets in half as much light at the none below it to allow for easier exposure calculations. There are two types of shutters. One is an opening in the camera lens and the other is a curtain, usually cloth or rubber, that moves accross the front of the film. The later is called a focal plain shutter.