Financial Power of Attorney ("Power of Attorney" or "Durable Power of Attorney" or "POA")

A legal document in which you authorize another person to make financial and some legal decisions on your behalf during times when you cannot make the decisions for yourself. Every person 18+ needs this.
 

Healthcare Power of Attorney ("Advance Directive for Health Care" or "Living Will")

A legal document in which you authorize another person to make your medical decisions on your behalf, including whether you want life support in certain circumstances. This document is used while you are alive, but cannot care for yourself and cannot communicate your wishes to others. This is arguably the most important of the estate planning documents.

Health Insurance Portability and Accountability Act ("HIPAA") Authorization aka "Medical Release Form"

A document authorizing another person to access your medical records, and granting permission to medical providers and facilities to release the records to the named authorized person/people.