Air flows from high to low pressure. The bigger the pressure difference over a distance, the stronger the wind. On a weather chart you see this in the isobars: lines joining places with the same air pressure.

But the earth turns underneath the moving air. That deflects the wind: to the right in the northern hemisphere, to the left in the southern hemisphere. This apparent force is called the Coriolis force.

Above the friction with the ground, from about 2,000 ft, the wind is deflected so far that it blows along the isobars instead of across them.