Brain death is a legal and medical term used to describe the irreversible loss of all brain function. This means that the brain is no longer functioning and cannot be revived. A brain-dead person is legally and medically dead.There are two types of brain death:1. Coma – A coma is a state of unconsciousness where a person cannot be awakened and is unresponsive to external stimuli. A person in a coma is not brain-dead.2. Vegetative state – A vegetative state is a state of unconsciousness where a person can occasionally open their eyes and may appear to be awake but is unresponsive to external stimuli. A person in a vegetative state is not brain-dead. Brain death is a legal and medical term used to describe the irreversible loss of all brain function. This means that the brain death is usually caused by an accident or severe illness that results in the loss of oxygen to the brain. This can happen if the heart stops beating, if the brain is injured, or if the person is suffocating. However, it is also possible for a person to be brain dead while still breathing and with a heartbeat. This can happen if the brain is so damaged that it can no longer control the body's vital functions.