A Power of Attorney is a legal document where one party (the Principal) authorizes another party (the Agent or the Attorney-in-fact) to act on his or her behalf during an absence. This authority can specifically include or exclude several areas of interest, including matters of physical property, real estate, banking, insurance, tax matters, etc.
Traditionally, this authority ends when you become medically incapacitated. However, you have the option to make the Power of Attorney (1) "Durable" which means it will remain effective from the time of signing the document and if you become medically incapacitated; or (2) "Springing" which means it will only be effective upon you becoming medically incapacitated.