General Power of attorney is a mandate or authorization to someone to act in somebody's behalf in a business or legal matter. Here the person who authorizes another to act on his behalf is the granter and the person who is authorized to act becomes his agent, in law he is referred to as an attorney.
General Power of attorney can be oral and could be witnessed or could be not, but it will hold in the court of law, in a same ways as it was in the main document. In some cases law requires the power of attorney to be executed in writing. Many of the institutions like banks, hospitals and US Internal Revenue Service requires power of attorney in writing. They usually keep the original copy for their records. Some of the countries have made electronic power of attorney a valid document.
Equal dignity rule is a principle law which demands a validity and authorization for performing some actions for other person who has been appointed in a same way as required by the act. This would mean that if the executor authorizes somebody to sell the executor's house and the law of land demand that the sale contract is to be in writing, then the authorization of that other person to sign the sales deed must be in writing also.
A General power of attorney could be special or may be limited to one act or types of act. A person who holds a power of attorney is referred to as attorney general. A power of attorney becomes null if the executor dies or is declared invalid unless of course the grantor specifically indicates that this attorney will then also continue. In that case such power of attorney is known as durable power of attorney. Do not forget that it is always better to choose the right person to hold this position of power and immense responsibility.