Final answer:
Wind is the movement of air caused by the unequal heating of the Earth's surface. It occurs when air moves from areas of higher pressure to areas of lower pressure. This movement of air is called air mass.
Step-by-step explanation:
Wind is the movement of air caused by the unequal heating of the Earth's surface. The sun's energy heats the Earth unevenly, causing areas to have different temperatures and pressures. Air moves from areas of higher pressure to areas of lower pressure, creating wind. This movement of air is called air mass, and when it moves horizontally, it is known as horizontal wind.