The horizontal movement of air form high pressure regions to low pressure regions is called wind. Steady winds blow from subtropical high pressure belts to equatorial low pressure belts (trade winds) and from subtropical high pressure belts to subpolar low pressure belts (westerlies).
Similarly, polar winds blow from polar high pressure belts to subpolar low pressure belts.
Due to the variations in the distribution of solar energy received and the rotation of the earth, variations occur in the pressure belts formed. This is the reason for the formation of winds.