"The Disclaimer" - The following is a summary/outline and does apply to your particular situation and is not legal advice. It's general information.
A Living Will is a document that allows you to make end of life decisions while you are competent to do so. First, you are making the decisions that if you are on life support and there's no reasonable hope for your recovery, then its okay to remove the life support and/or discontinue medical treatment except for pain and comfort care and allow you to die.
Furthermore, a section in the Living Will deals with the withdrawal of artificially provided food and water, and your decisions regarding that issue. Finally, you make decisions regarding organ donation after your death.