Someone to Represent or Help You When You Can’t Help Yourself
There are two types of Powers of Attorney – “Limited Power of Attorney” and “Durable Power of Attorney.” 
A Limited Power of Attorney allows you to appoint a person to act on your behalf for a specific reason or for a specific period of time. You may be selling a home and may be unable to attend the closing. You could use a Limited Power of Attorney to allow an agent to sign the documents in your behalf.
A Durable General Power of Attorney allows you to appoint a person to act on your behalf if you become physically or mentally incapable of handling your affairs. In a Will, you appoint an executor or executrix to handle your estate after you die. An executor cannot step in until a death occurs. You appoint an agent in your Power of Attorney to handle your affairs while you are alive, but unable to handle them yourself.
The Power of Attorney is void upon your death. A Power of Attorney can also be revoked at any time. A new person may be named by the preparation of another Power of Attorney.
You generally appoint a family member or a trusted individual as your agent as well an alternate agent.
Should you be unable to manage your own affairs and do not have a General Durable Power of Attorney in place, an application to the Court may be necessary to name a guardian for you. The proceedings of this type can be extremely expensive and time consuming. You also risk the possibility of having a person named as your guardian that you would not otherwise select yourself.
Your best protection is to have a Power of Attorney prepared while you can still make decisions yourself. You then pick the person that you feel is most capable to step into your shoes.