A concussion is a type of mild traumatic brain injury (TBI). The term "TBI" covers brain injuries of varying severity, from mild to severe. Concussions are at the mild end of the spectrum and are characterized by a temporary alteration in brain function caused by an external force. Although most people recover fully from a concussion, the brain is vulnerable to further injury during the recovery period. Severe THIs can involve prolonged unconsciousness or amnesia after the injury, and they often have more significant and long-lasting effects on cognitive, physical, and emotional function.