You go outside and try to use your receptacle located at the front or rear of your home and you find it dead. First thing that comes to your mind is that a circuit breaker has tripped and it will simply be a matter of going to your electrical panel and resetting the breaker. You take a look at your panel and all of the breakers are on, nothing is tripped. Now the situation looks more complicated. Do you call an electrician? Not necessarily. There are a couple of things you can check before it really gets to the point of needing an electrician. If your home is older than approximately 10 to 15 years your outside receptacles may be connected to your bathroom receptacles that are protected by a receptacle called a GFI receptacle. GFI stands for Ground Fault Interrupter which is just what it does. If any of your receptacle wiring faults to ground, either through you or some other type of ground fault, the receptacle will trip and take all receptacles down the line from it out too. So check your bathrooms until you find a GFI receptacle that is tripped and reset it. Some electricians installed the GFI at the outside location and fed the bathroom receptacles from there so keep in mind the problem can be in either of those locations. The third possibility is a GFI located in the area of the electrical panel. Outside receptacles were sometimes fed from this location. Knowing what receptacles are on a circuit together and which receptacles need to be protected by GFI's will help you solve a outage yourself and save the cost of that service call from your local electrician.
Source: Electrical Wiring Tips
