what is exactly a thermal wind????? please elaborate... what is a wind shear???

Thermal wind is the difference in wind over different layers of atmosphere due to horizontal temperature difference. It is not exactly wind but a wind shear which means difference in wind speed over a certain short distance in the atmosphere.

 

The phenomenon is governed by an equation which relates the geopotential thickness of the atmospheric level and different pressures at those levels. This is beyond the scope of grade X and hence cannot be elaborately explained. If needed this concept can be referred over different sources on the internet.