GFCI outlets are special outlets that detect any surge in the power line. If a surge is detected, the GFCI outlet actually cuts off the power to the entire electric circuit in which the surge was detected. So if you or someone else in your home accidentally drop an electric can opener or a hairdryer into a sink or bathtub filled with water, the GFCI will automatically shut off the power for that circuit. Current building codes require GFCI outlets in the kitchen and bathroom of new homes, but if your house doesn't have GFCI outlets, you can buy them at your local hardware store or home center. You can install a GFCI outlet yourself--just be sure to shut off your power at the breaker box before working with electricity--or you can hire an electrician to install the GFCI outlet for you.
Not every outlet in your home needs to be a GFCI. One GFCI outlet per electrical circuit is sufficient. But how do you know if outlets in your home are GFCI protected? GFCIs have a red test button and a black reset button. If the red test button pops out of the outlet, that indicates a surge has been detected and the circuit shut down. Every outlet on that same circuit will be GFCI protected, even if it doesn't have the red and black buttons. In many new homes, a blue "GFCI Protected" sticker let's the homeowner know they're protected, but if you're not sure whether your outlets are GFCI protected, you can plug a small electrical tester into each outlet.
There are certain appliances you won't want to have plugged into a GFCI circuit. Since refrigerators, freezers, garage door openers and lawn sprinklers have periodic power surges, they will trigger the GFCI which will shut down the circuit. If power is shut off to your refrigerator or freezer while you're at work, you could come home to spoiled food!
But do make sure you install a Ground Fault Circuit Interrupter in your kitchen, bathrooms, utility room, garage, and any outdoor outlet that comes in contact with water. They will protect your and your family!