The differences between the two categories of power of attorney have to do with when the power of attorney goes into effect and when it ends, and whether the person
granting the power of attorney (the grantor) also retains authority over his or her own affairs.
A power of attorney goes into effect as soon as it is signed (or on some other specific date noted in the document) and can be ended (revoked) by the person granting the power of attorney at any time that he or she remains mentally competent (or on a specific date noted in the document). The granting of a power of attorney does NOT remove the grantor's authority over his or her own affairs. Instead, it give the authority to someone else to also make decisions if and when the grantor does not.
A durable power of attorney, on the other hand, remains in effect if and when the grantor becomes incompetent to make his or her own decisions. Often durable powers of attorney are written so that they go into effect ONLY if the grantor becomes incompetent. These types of documents are often referred to as "springing" powers of attorney because they only "spring" into effect if the grantor can no longer make his or her own decisions.
A power of attorney can be general or specific. A general power of attorney gives the agent authority in all situations and for all purposes (except for those specifically excluded in the document). A general power of attorney does not, however, mean that the grantor gives up authority over his own affairs. As long as he or she is mentally competent, the grantor can also make all his or her own decisions.
A specific power of attorney document gives authority only in specific situations named in the document, such as buying or selling a business or property, making gifts or donations, collecting debts. A specific power of attorney remains in effect until a particular date stated in the document, until the named transactions are completed, or until the principal becomes incapacitated, dies, or revokes the document.
Also, in some states a medical directive -- permitting a family member or other person to make medical decisions for someone when they become incapacitated -- is also called a power of attorney for health care. This type of power of attorney goes into effect if and when the grantor becomes incapacitated, either temporarily or permanently and is limited to decisions relating to medical care.