A stroke happens when you have a loss of blood supply and oxygen to brain cells. So, you have an interruption of blood flow to your brain and brain cells die. Ischemic stroke which is a sudden stop in the flow of blood through the blood vessel in your brain, and that can be caused by clots in the blood vessel, or the blood vessel has clotted down and the blood can’t get through, or a hemorrhagic stroke which means a blood vessel has broken open and blood is pouring out into your brain where it shouldn’t be.