Why does the wind happen?

Question

Why does the wind happen?

Answer 1

The wind is caused by differences in air pressure - air moves from the highest pressure to the lowe pressure - and that movement causes wind

Answer 2

It's caused by differences in air pressure,  which are caused by unequal heating of earth's surface.  Air flows from hight pressure to low pressure,  with deflection caused by the rotation of the earth.  

Answer 3

Wind is the flow of air or other gases that compose an atmosphere (including, but not limited to, the Earth's). It occurs as air is heated by the Sun and thus rises. Cool air then rushes to occupy the area from which the hot air has just moved. It could be loosely classed as a convection current.