Electrical Service is the incoming power line that feeds switches, outlets, and appliances throughout your home. It is usually rated in amps (a measure of the flow rate of electricity) and voltage (the pressure to run the wires), with varying sizes for different homes and equipment loads.
The main service wires are a pair of ungrounded conductors fed from the utility company’s overhead line to a weather head, mast, or meter socket. The meter is a watt measuring device supplied by the electric company that keeps track of each month’s consumption. Next to the meter is often a disconnect, or safety switch as per National Electrical Code requirements. This allows the homeowner to kill the incoming power from outside without having to go inside the house. This is very important in the case of a tree falling onto the main service line, or even a lightning strike which may send a huge amount of excess current to the conductors at the service point and burn them out.
Overhead power lines are still used in many places, but newer residential construction uses buried lines called a service lateral. These are safer for homeowners because they are not subject to the weather and nature, and they are more aesthetically pleasing.
The next piece of equipment is the main breaker panel, also known as a fuse box or service panel. This is usually a gray metal box located in a basement or garage, or contained inside a finished cabinet mounted on an exterior wall. From here, the two ungrounded wires (hot legs) and one grounded conductor from the meter drop enter the main breaker panel and are separated into individual circuits which power the switches, outlets, and appliances within the home.