A GFCI outlet is a receptacle with a built-in ground-fault circuit interrupter that compares current on the hot and neutral conductors and cuts power within a fraction of a second if about 5 milliamps leak to ground, such as through water or a person. The NEC requires GFCI protection in kitchens, bathrooms, garages, outdoors, and other damp locations.
Why it matters to you
GFCI protection prevents shock injuries where water and electricity meet, and because the devices can wear out without any visible sign, an untested GFCI may no longer be protecting anyone.
Practical guidance
Press TEST monthly; the outlet should click and cut power, and RESET should restore it. If a dead bathroom or kitchen outlet has no buttons, look for a tripped GFCI upstream on the same circuit, often in another bathroom, the garage, or outdoors, and replace any GFCI that will not trip or reset.