GFI - Ground Fault Interrupt. On each circuit you will find several duel, plug-in receptacles. All but one receptacle will be the common, non-GFI type. One receptacle will be a GFI receptacle. Between the two plug in points on the front of the receptacle there will be two buttons - little square buttons on mine. One button is to cause a power interruption, the other button is to reset it. When a GFI has been interrupted, much like a breaker on a panel has been kicked into its interrupt state, the reset button will slightly protrude out and away from the flat face of the receptacle. Simply push in the button, about 1/8th of an inch, to reset it. If it will not hold the reset, then you likely have a short somewhere in the circuit, or have a device plugged into a receptacle on the circuit that is drawing too much electricity for the capacity of the GFI and its circuit.