A more thorough explanation:

A letter of attorney is a legal document that grants someone else the power to act on your behalf. This person is called an attorney-in-fact or agent. The letter of attorney can be used for a variety of purposes, such as managing your finances, making medical decisions, or signing legal documents.

John is going on a long trip and wants his sister to be able to handle his finances while he's away. He writes a letter of attorney giving her the power to access his bank accounts and pay his bills.

Mary is in the hospital and unable to make medical decisions for herself. She writes a letter of attorney giving her daughter the power to make medical decisions on her behalf.

These examples illustrate how a letter of attorney can be used to give someone else the legal authority to act on your behalf. It's important to choose someone you trust to be your attorney-in-fact and to clearly outline their powers and responsibilities in the letter of attorney.