Stroke is situation that occur the blood flow to the brain disturbed or less due to blockage of blood flow (ischemia stroke), or blood vessel burst (hemorrhagic stroke). Without the blood, the brain is not getting supply oxygen and nutrition. So that the brain cells dysfunction or die partly at area of vessel has been broken. That situation makes partly the body that given role motoric functions become dysfunction eg paralise.
Stroke is emergency medical state because the brain cells die in few minutes if it insufficiency blood supply happened. So it needs treatment or surgery as soon as possible to reduce damages of the brain cells.