When you look around, the images that you see are a result of light bouncing off of objects and then entering your eyes. Cameras capture this light in several ways. In the past, cameras contained rolls of film on the inside. The film contained chemicals which would react with light and change color. When you took a picture, the camera would let the light in for a short amount of time. The chemicals in the film would react with the incoming light and change color, with brighter light causing the film to become darker. This produced what was called a negative, a reverse image of the picture that you took, where bright sections of your picture are dark and dark sections are bright.

To convert the negative image to the actual photo, the negative was taken to a room, called a darkroom. In the darkroom, light is made to shine through the negative onto another sheet of paper treated with chemicals, which react with the light and produce the true image on the paper.

This process for taking pictures took a long time to produce the final picture, so eventually the Polaroid Corporation invented a camera which combined all the chemical steps into the camera and produced the picture immediately. These cameras were called Polaroid cameras, or instant cameras.

Today, most cameras work in an entirely different way. When you take a picture, light enters the camera and hits a grid of thousands of crystal photosites. Each photosite absorbs the light energy, and converts it into an electrical signal. This electrical information corresponds to the brightness of light at that part of the picture. The brightness information from each photosite is then sent to an inkjet or laser printer for printing.