Last Will and Testament is the document that appoints the executor for your estate and names your primary and contingent beneficiary. A well drafted Will will save money and heartache.
Power of Attorney authorizes another person to act for you if you are unable to act yourself. This power can be broad or narrow, and multiple people can be named for different situations.
A Directive to Physician, or Living Will, provides instructions for your medical care. Many times these are end of life situations and very difficult.
A Trust is a contract with another person called a Trustee to administer funds as you designate. It is vital in a range of situations but rarely used for tax purposes today.