An Automated External Defibrillator (AED) is a portable, user-friendly medical device that analyzes a person's heart rhythm and, if necessary, delivers an electric shock (defibrillation) to restore a normal heart rhythm during a sudden cardiac arrest. They are designed for use by anyone, not just medical professionals, and provide audio and visual prompts to guide the user through the process. AEDs are found in public places like schools, airports, and offices to provide immediate treatment before emergency services arrive.