First electricity is generated at a power plant.  By wire, it then goes to a transformer that "steps up" the voltage.  Power plants increase the voltage because less electricity is lost along electric lines when it’s at a high voltage.  Then the electricity is sent on a nationwide network of transmission lines.  Transmission lines are the big tower lines you see when you’re driving down the highway.  The lines are interconnected, so if one fails, another one will take over the load.  Electricity then is carried over distribution lines that deliver electricity to your home.