An ordinary power of attorney (OPA) is a legal document that allows someone to act on your behalf in specific situations for a temporary period. 

Purpose

You can use an OPA to give someone the authority to make decisions or act on your behalf for example when you're overseas or perhaps you have had an accident and become immobile for a time.  For example, you can give someone the power to pay bills or send you money from your accounts. 

Duration

An OPA is created for a defined period of time and ends if you lose legal capacity. 

Who's involved

You are the ‘donor’ of the power, and the person you give the power to is your ‘attorney’. You can choose your attorney, the powers you grant them, and how they should be used.  But it is important to note that the donor must have capacity to give the power of attorney.

Witnessing

Both the donor and attorney must have their signatures witnessed by someone over 18 who is not related to either party and who does not benefit from the power of attorney.  The same witness can not act as a witness for both the donor and the attorney.

An OPA is different from an enduring power of attorney (EPA), which remains in effect even if you lose your capacity.