A living will (also called a "health care directive" or "advance directive") is a document by which an individual may decide to accept or refuse any medical treatment. A competent individual has the right to determine what medical intervention he or she wants.
By means of a living will a person can give detailed instructions as to exactly what treatment is to be rendered in specific situations.
Commonly, a living will is used to express a person's decision not to be kept alive artificially if he or she has suffered substantial and irreversible brain damage. This is sometimes referred to as being in a "permanent vegetative state" or being "brain dead."
With a living will a person can make decisions as to the use of ventilators, surgery, resuscitation (CPR), drugs, tube feeding, pain medication, etc.