Wind
Wind is the horizontal movement of air from areas of high pressure to areas of low pressure, driven by uneven heating of Earth's surface.
Definition
Wind is moving air, blowing because the Sun heats different places unevenly, sending air from where pressure is higher toward where it is lower, and the greater the pressure difference over a given distance, the stronger the wind. Earth's rotation deflects moving air through the Coriolis effect, to the right in the Northern Hemisphere, which organizes global wind belts into trade winds, prevailing westerlies, and polar easterlies, while local winds such as sea breezes form from the same uneven heating on a smaller scale. Above the friction of the surface, the balance between the pressure gradient force and the Coriolis force produces geostrophic wind parallel to isobars, and jet streams reaching over $100\ \text{m/s}$ arise from the thermal wind relation that ties vertical wind shear to horizontal temperature gradients.
Example
A sea breeze blows in from the ocean on summer afternoons because land heats up faster than water, and the rising warm air over land pulls in cooler air from the sea, while a north wind, named for the direction it comes from, blows from north to south. The prevailing westerlies carry weather across the United States from west to east, which is why storms usually reach Charlotte from the west, hurricane winds spin counterclockwise around the eye from the Coriolis effect, and wind power scales with the cube of wind speed, which is why North Carolina's best wind resource sits offshore near the Outer Banks.
Key Insight
Wind is essentially convection turned sideways, with warm air rising in one place, cold air sinking somewhere else, and wind supplying the flow along the ground that connects the two. It exists because the Sun keeps creating pressure differences that the atmosphere is always trying to erase, and if solar heating stopped, winds would die out within days as the pressure field flattened.