How do tractor-type farming vehicles exactly harvest and partially process grains?

Question

How do tractor-type farming vehicles exactly harvest and partially process grains?

Answer 1

They're called combines.

http://en.wikipedia.org/wiki/Combine_har...

Answer 2

First there is a cutting bar which cuts the stalks near the base .  These are then fed into a sort of shaking device where the grains fall from the heads, fall through a sieve type sheet and then transferred to a tank.  The remaining stalks (straw) is passed through and out the back.  The grain in the tank is then periodically emptied.