What does it really mean when you "take" a picture with a camera? When you click the shutter, you have frozen a moment in time by recording the visible light reflected from the objects in the camera's field of view. In order to do that, the reflected light causes a chemical change to the photographic film inside the camera. The chemical record is very stable, and can be subsequently developed, amplified and modified to produce a representation (a print) of that moment that you can put in your photo album or your wallet, or that can be reproduced millions of times in magazines, books and newspapers. You can even scan the photograph and put it on a Web site.
To understand the whole process, you'll learn some of the science behind photography -- exposing the image, processing the image, and producing a print of the image. It all starts with an understanding of the portion of the electromagnetic spectrum that human eyes are sensitive to: light.