How is elevation represented on a topographic map?

In order to "map" a terrain a cartographer needs to know how high or how low the soil is (land) from sea level. The physical makeup of earth, the physical map of places shows you land formations through the use of color which codes the particular place as being a certain distance above sea level. If the map was coded so that low elevation numbers (valleys) are dark and high elevations (mountains, peaks, plataues) are light, what you end up with is an image (likely shaded) which represents the "relief" of the place. Relief means 3 dimensional or sculptured in art. You can think of a map as a kind of art of the 3 dimensional physical world.