What is a GFCI receptacle or outlet? You may have heard the term GFCI or GFI before when dealing with electrical receptacles, especially if you have had a home inspection. GFCI stand for Ground Fault Circuit Interrupter. A GFCI receptacle measures current coming from the hot slot, or the smaller slot, and compares it the the current returning the the neutral slot, or the larger slot (assuming the outlet was wired properly). If it senses that the current leaving and the current returning are different then it will trip and shut power off to the outlet.
GFCI receptacles should be located in bathrooms, kitchens, laundry rooms, all exterior outlets, and garages. Basically any place where water is near or where there is potential for water to be near the outlet.
I made a video here to explain what a GFCI receptacle is and a demonstration of how they work. Enjoy!