Air is a mixture of gases and water vapour. Moving air is called wind. A light wind is called a breeze. The wind is the movement of air caused by the uneven heating of the earth by the sun and the earth's own rotation. It does not have much substance-you cannot see it or hold it — but you can feel its force. It is the great equalizer of the atmosphere, transporting heat, moisture, pollutants, and dust at great distances around the globe.