A concussion is a temporary functional disturbance of the brain resulting from biomechanical forces, such as rapid acceleration or impact. It is classified as a type of traumatic brain injury and affects the brain's ability to process information normally. The mechanism of injury causes temporary changes in brain metabolism and neural function, rather than physical damage to the tissues. Symptoms can vary widely but commonly include headache, dizziness, nausea, memory difficulty, and altered levels of consciousness or alertness. Recovery is generally considered gradual, requiring time and rest to allow the brain's normal regulatory systems to restore equilibrium and function.