An AFCI breaker is a circuit breaker with a built-in arc-fault circuit interrupter that monitors the current waveform for the signature of dangerous arcing, such as from a damaged cord, a loose connection, or a nail through a wire, and trips before the arc can start a fire. The NEC requires AFCI protection on most living-area circuits in new homes.
Why it matters to you
Arcing faults are a recognized cause of home electrical fires and often happen inside walls where nobody can see them, so AFCI protection catches hazards that a standard breaker sized for overloads can miss.
Practical guidance
Press the TEST button on each AFCI breaker monthly or as the manufacturer directs. Occasional trips from older vacuums or motors happen, but a circuit that trips repeatedly should be diagnosed by an electrician, never fitted with a standard breaker to make the tripping stop.