Threshing is done to take out the grain from its outer covering called chaff.
In the traditional method of threshing,the harvested crop is spread on the ground in a small area and various cattle are made to walk over it again and again in a circle.The cattle’s feet crush the harvested crop plant due to which the chaff breaks up and the grain comes out.
A motorised machine called thresher is also used for the threshing process.
The process of separating grain from chaff and hay with the help of wind is called winnowing.
When the grains mixed with chaff and hay is made to fall from a height in blowing wind,the grains,being heavy falls straight to the ground whereas the chaff and hay being much lighter are carried some distance away by the wind.