The Camera’s Eye
A camera lens is the “eye” of a camera, allowing it to see the outside world. It also works a lot like a human eye, in that light passes through the lens and is focused on the film or image sensor of a digital camera. This light carries the images that both you and camera see.
A lens has several elements inside a metal barrel. Each element is actually a simple lens itself–a piece of carefully shaped and polished glass. The glass elements in the lens are what focuses the image for the film or sensor.