The GFCI is a fast-acting circuit breaker that senses small imbalances in a circuit caused by any leaking electric current and shuts off the electricity instantly. You can recognize GFCI outlets by the test and reset buttons located on them. GFCIs are found in newer homes. They are required in kitchens, bathrooms, garages and basements. In older homes, they can be installed by an electrician as a replacement outlet. Portable GFCIs are also available.
The round plug on a three-pronged plug connects to a ground wire inside the outlet. If the outer surface of an appliance or tool becomes energized, electricity will travel to ground through the ground wire, rather than through you. Never modify or remove the third prong.
Any outdoor outlet must be weatherproof and have a GFCI to protect you from serious shock. If you run an extension cord from an indoor outlet to work at an outdoor location, choose an outlet that has GFCI protection.