A GFCI (ground fault circuit interrupter) is a type of receptacle which shuts off electric power when it senses an imbalance between the outgoing and incoming current. The main purpose is to protect people from an electric shock caused when some of the current travels through a person's body due to an electrical fault such as a short circuit, insulation failure, or equipment malfunction. Standard receptacles shut off power when the current is too high, like 10, 15, or 20 amps by a breaker, but a mere 0.030 amps through a body can cause paralysis of skeletal muscles and stop the human heart. The GFCI receptacle breaks the circuit when it detects an imbalance of only 0.005 amps.

A GFCI receptacle can also prevent fires from short circuits and other electrical faults that don't involve humans such as a low current short where the current never reaches the trigger point for a circuit breaker , e.g. a live wire falls in a tub of water or moist soil and only 1 or 2 amps of current flows.

A GFCI outlet takes the place of a standard outlet in any location that may be exposed to moisture. It is identifiable by the addition of two buttons to control the GFCI functions, labeled “Test” and “Reset.”