<human>:  What is the difference between a cloud and a fog?
<bot>: The primary difference between a cloud and a fog is that clouds are formed higher in the atmosphere and are composed of tiny droplets of water or ice crystals that are held afloat by warmer air temperatures. Fogs, on the other hand, generally form close to the ground, as the warmer air that rises from the surface of the Earth rises and comes in contact with the cooler air high above. The two phenomena are often confused because of confusion between clouds that form low in the sky, look very similar to a fog.