In plain English: the person granted authority — by power of attorney — to perform certain acts in your name and on your behalf if you are unable or unwilling (or simply choose not) to act for yourself.
The title: “attorney-in-fact” does not need be a lawyer. It is the person you trust to step into your shoes for the acts described in the document — nothing more, and only within the four corners of the document.
What a good agent does: acts loyally, keeps their own money separate from yours, and stays within the powers the document grants. They can be a spouse, adult child, friend, or professional.
Watch out for: naming the wrong agent is dangerous — they can move your money. Name someone trustworthy and organized, and consider naming a monitor or co-agent if you’re worried about abuse. A POA is powerful; choose carefully.