A lens to collect the light reflected from a subject and form an image on the film. The size of the lens opening may be fixed or it may be adjustable. A shutter to control the length of time that light reaches the film. The shutter keeps light out until you take a picture. Simple cameras have one or two shutter speeds.
Advanced cameras have a wide range of shutter speeds.
A fast shutter speed allows you to capture action scenes. A shutter release to open and close the shutter. A film-advance mechanism to advance the film for the next exposure. A viewfinder to show you the area you are taking pictures of. Some cameras have a built-in flash, while others have a flash shoe for holding a flash accessory.