The power to your home and the electrical systems inside are critical to your home operating smoothly. Think about the last time the power went out and how everything shut down. It is a good practice to periodically have a professional electrician check your systems such as circuit breakers, fuse boxes, meters, connections to other key equipment and general wiring. A periodic check-up can help spot potential trouble before it occurs.
The electrical system in your home depends on when it was built and if an electrical upgrade was ever done. Building codes have changed over time implementing more safety features when it comes to electrical systems such as grounding wires and ground fault interrupter outlets and circuits.
Here is a good overview of electrical systems by homeownerseries.com