A stroke occurs when the blood supply to part of the brain is disrupted, depriving brain cells of oxygen. There are two main types of stroke: ischemic, caused by a blockage, and hemorrhagic, caused by a ruptured blood vessel. Symptoms vary depending on the affected brain region but may include numbness, weakness, vision problems, confusion, and trouble speaking. Immediate treatment involves calling emergency services, monitoring the person's condition, and preventing movement until medical help arrives.