I assume that, by A.I.F.. you mean attorney in fact.
A Power of Attorney is... well, it is a power to act on another's behalf. It is an abstraction. But, in common usage, it is often used to refer to the document that spells out the power and/or the person to whom the power is granted.
The person who grants the power of attorney is the "principal." The person receiving the power is the "agent" or "attorney in fact."
Also how severe can the penalties be for abusing either?
Depends upon the nature and severity of the abuse. Could be having to return any funds to the principal up to and including jail time.