A brain injury occurs when there is damage to the brain, which can result from various causes such as a blow to the head, a fall, or a stroke. These injuries can affect how the brain functions, leading to problems with thinking, memory, movement, and emotions. There are two main types of brain injuries: traumatic brain injury (TBI), which is caused by external forces, and acquired brain injury, which occurs due to internal factors like lack of oxygen or infections. Treatment and recovery depend on the severity and type of injury, and rehabilitation may be necessary to regain lost skills.