A concussion is a type of brain injury. The brain is made of soft tissue and is surrounded by a cushion of spinal fluid. The skull surrounds the brain and protects it. A person can injure their brain by getting hit on the head, or even the body, resulting in the brain moving around in the skull. This can lead to bruising of the brain, damage to blood vessels, and injury to nerves. People can get a concussion from a fall, a car crash, or a sports injury.