What is an arc fault?
A ground fault, or a short circuit, happens when a live wire comes into contact with a ground – that ground can be a neutral wire or it can be a human body. Circuit breakers and GFCI outlets protect people from serious shock from ground faults.
An arc fault, on the other hand, occurs when a loose or corroded connection or exposed wire makes contact and causes arcing between the connections. Because circuit breakers are designed to trip when a ground fault happens, an arc fault may not trip the circuit breakers, and so pose a serious danger of electrical fire.