This type of image shows heat based radiation from the infrared
spectrum. In other words, the warmer the surface, the more
infrared radiation it emits. For a satellite image, cooler
surfaces are bright and warmer surfaces are dark. Since the
atmosphere cools as you increase in altitude, clouds would show
up as bright areas and land surfaces as dark areas. In addition,
low clouds will be more gray and higher clouds will show up more
white. Tall thunderstorm clouds will show up as bright white and
fog will be hard to discern from land areas. A large advantage
of IR is that you can view it 24 hours a day.