Medical Directives are legal documents that explain your treatment wishes to medical professionals. There are two common types:
Living Will
A written statement, signed by you, wherein you tell your doctor and other medical personnel what type of medical treatment you desire in the event your doctor determines that you are terminally ill and that your death is imminent.
Power of attorney
A written authorization whereby you permit a trusted family member or trusted friend to make medical decisions for you when you are unable to make those decisions for yourself. One difference between a Durable Power of Attorney for Health Care and a Living Will is that the Durable Power of Attorney for Health Care allows your health care agent to make medical decisions for you even though you may not be terminally ill, yet are unable, due to your medical condition (such as a coma), to make and communicate your medical decisions to your doctor or other medical personnel.