Wind is the movement of air around the earth. It is basically caused by the uneven heating of the earth's surface. Warmer, lighter air is pushed along by heavier, cooler air. Other factors affecting wind include whether the particular place is close to land or water, the seasons of the year, the topography of a place, etc..
Wind direction is measured by a wind vane which is an arrow mounted on top of an elevated site. The wind vane is designed so that its arrow points into the wind. With a compass aligned with the arrow, one can determine the direction of the wind.
Wind speed or velocity is measured with either an anemometer or radar. The anemometer, pictured above, consists of several cups mounted sideways and extended out on a rotating axis or pole. The cups catch the wind and the more turns of the attached cups, the greater the wind speed.
Doppler radar is also used to measure wind speed. It works like a police radar gun aimed at speeding cars, but in this case is aimed at speeding winds with microwaves.
A scale for measuring wind speed is called the Beaufort scale. On this scale winds are ranked from the calmest air movement at 0 to hurricane winds at 12. calm, light air, light breeze, gentle breeze, moderate breeze, fresh breeze, strong breeze, moderate gale, fresh gale, strong gale, whole gale, storm, hurricane