What is a "GFI" outlet?

 Ground Fault Interrupter Outlet

Ground fault circuit interrupters are receptacles that are designed for use around water or outdoors power requirements. Kitchens, bathrooms and any outside outlets should have GFCI protected outlets installed. These receptacles measure the amount of incoming and outgoing current and will trip out if there is a difference in the amount. This amount should be the same on what comes in on the hot side and leaves on the neutral. If not there is a ground fault and the receptacle will trip and shut down the power for safety purposes.
If you do not have GFCI protected outlets installed in your home then you really should have this work done for the safety of everyone in the home.