A ground fault circuit interrupter (GFCI), or Residual Current Device (RCD) is a device that shuts off an electric power circuit when it detects that current is flowing along an unintended path, such as through water or a person. It is used to reduce the risk of electric shock, which can cause the heart to stop or cause burns. They can also prevent some fires, like when a live wire touches a metal conduit.

ground-fault circuit-interrupter breaker

ground-fault circuit-interrupter outlet