Its a pity people feel the need to answer questions when they really have no idea what the correct answer is. There are different types of power of attorney and for a better insight into what they are I suggest you try the link below.
letter of authorization allows someone to act on your behalf...power of attorney gives soemone power over all decisions regarding you or your health. it gives them the right to make decisions about your life or death...its a very different thing. dont do it unless you are seriously ill and dont think you will be able to decide for yourself in the future.
參考: My mom has worked for attorney's for the last 20 years!