A Power of Attorney is a legal document you use to allow another person to act for you. You create a legal relationship in which you are the principal and the person you appoint is the agent. A Power of Attorney specifies the powers you give to your agent. The powers can be limited or broad. For example, if you are selling your house, but unable to attend the closing, you can give someone the power just to sign the deed in your absence. Most durable powers of attorney, however, give your agent the power to do almost anything you could do.
Banks, brokerage firms, and other financial institutions may require you to sign one of their own forms. The law requires that these third parties accept the power of attorney if it its acknowledged and provides for a process for verification if there are still questions.