First and foremost is the difference in air temperature. We all know heat rises. When the sun heats the earth it warms the air above it causing it to rise. Cool air replaces the rising hot air and we have wind. You can observe this in the ripples that form on a lake as the rising sunwarms the early morning air.
Looking at the wind on a global scale we see this hot air rising from the equator and moving north. As it cools it falls back to the earth’s surface. This atmospheric circulation pattern known as a Hadley Cell - low pressure and converging winds, plus something known as the Coriolis effect - produces what are known as tropical easterlies or “trade winds.”