Defibrillation
Defibrillators are machines used my paramedics to re-enable your heart it it stops. Two insulated handles are charges from a high voltage supply, and are put in electrical contact with the patients chest. No one else can get the shock while it is being transferred to the patient. This is why the paddles have insulating handles. Then the charge is passed through the patient to make their heart contract.
Defibrillation is a treatment commonly used when someone has a life threatening cardiac arrest. It delivers electrical energy to the heart. It allows the normal heart rhythm to be reestablished. The shock that is delivered is very high voltage, so all by standers mush move away. Even bystanders will be able to do this, because it does not require any training at all. defibrillators can be external, Transveneous, or implanted.
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Defibrillator
Defibrillators are an external method to reestablish the heart's pulse.
AED
Automatic External Defibrillator
Uses an electrical shock that transfers through the patients body.
When the electrical shock is given to reset the heart, the shock is given through metal paddles or patched applied to the outisde of the patients chest. It is an emergency procedure to re-enable the heart rhythm. The electrical shock is thousands of times stronger than the electrical current made by a pacemaker. This big shock can cause the patient's muscles to contract violently.
It is based on the understanding that the contraction of the heart, and the circulation of the heart. It is a medical technique used to transfer a shock, but it can be just as dangerous no its own.
Referencing:
http://en.wikipedia.org/wiki/Defibrillation
http://www.webmd.com/heart-disease/electrical-cardioversion-defibrillation-for-a-fast-heart-rate
http://www.resuscitationcentral.com/defibrillation/history-science/
http://www.sciencedaily.com/articles/d/defibrillation.htm
http://en.wikipedia.org/wiki/Automated_external_defibrillator