Also known as a GFI, a Ground Fault Circuit Interrupter is an inexpensive outlet or device that protects you from being shocked, burned, or from electrocution. It is not specifically made to protect an electrical device, it is made to protect people. It can also prevent electrical fires by interrupting electric current.
Constantly monitoring circuit flow, the GFCI normally interrupts power within 1/30th of a second, and is designed to shut off power before your heartbeat can be affected. Installed in all new homes, remodels, and updated in most bathrooms and kitchens, a GFCI is most often used near water sources (bathrooms, kitchens, unfinished basements, wet bars, laundry rooms, etc.). You can also purchase separate electric cords that have a built-in GFCI for when you are working in the yard or working with power tools.
GFCIs usually have a TEST button and a RESET button. If you find that an outlet in your home is not working, you might trace the source back to the nearest GFCI. Inexpensive (usually less than $15) and simple for an electrician to install or a qualified homeowner, if you are using any kind of appliance near any kind of water source, make sure that you have a properly functioning GFCI.
GFCI Outlets video provided by U.S. Inspect.