The techniques of dodging and burning date back to the dark ages, where film had to be processed and developed in a darkroom. In the dark room, photographers would dodge and burn when they enlarged a photo. Dodge out means to let less light on to the paper, lightening an area, and burning in means to add extra exposure time and more light to hit the paper, creating darker areas of an image.

Photoshop pays homage to these techniques in the toolbar. The buttons you press to lighten/darken a photo are reminiscent of the tools you would use in the darkroom. The buttons show a stick with a circular piece at the end and a cupped hand. The stick with the circular shape is the dodge tool, or lightening tool which would keep light from the paper and the cupped hand is the burning tool which lets more light into an area.