A power of attorney (POA) is a written document that gives another person the authority to act on your behalf. The person signing the document, or "Principal", appoints another person as an agent. The agent is also called an "attorney-in-fact", which is different than an attorney at law. A power of attorney may be oral and whether witnessed or not, will hold up in court, same as if it were in writing. For some purposes, the law requires a power of attorney to be in writing.