A cardiac defibrillator is a medical device used to restore a normal heartbeat in individuals experiencing life-threatening heart rhythms, such as ventricular fibrillation or pulseless ventricular tachycardia. It delivers an electric shock to the heart, which can help reset its electrical activity and allow it to resume a normal rhythm. There are two main types of defibrillators: automated external defibrillators (AEDs), which are designed for use by laypersons in emergencies, and implantable cardioverter-defibrillators (ICDs), which are surgically placed inside patients at risk of sudden cardiac arrest. Both types play a crucial role in emergency cardiac care.