A power of attorney is a legal document that lets you (the principal) appoint another person(s) (your agent or attorney in fact) to make decisions on your behalf. The specific terms of the power of attorney will describe what types of decisions the agent can make, including decisions about property, financial matters, health care, etc. The terms also determine how long the power of attorney lasts—a durable power of attorney is one that remains in effect if you are incapacitated.