What is a GFCI circuit breaker or outlet?

GFCI stands for Ground Fault Circuit Interrupter. It constantly measures the current on the hot and the neutral wire of a circuit. If the current in one of the wires differs from the other by 1/10,000 of an ampere the breaker or outlet trips. It does so because that 1/10,000 of an ampere is leaking and flowing somewhere other than through the wire and that somewhere could be someone’s body. These are used in wet locations throughout the house. Kitchens, bathrooms, outside, Garages, etc.