Wind is caused by air moving from an area of high pressure to an area of low pressure.
The surface of the earth is not the same all over and some surfaces produce more friction than others. So wind does not flow smoothly from place to place. Higher in the atmosphere the effects of the earth's surface are minimal and the wind speed is more constant. But gusts of wind are not a definable entity - like a water wave is, for example. A gust does not travel continuously through the air, as you will notice if you watch some leaves blowing around.