There are many separate circuits in a home that an electrician wires while the house is being built. Typically each room is on its own circuit with a separate breaker in the main panel. Various types of home equipment such as heating and air conditioning systems also have their own circuits. Additionally units such as a dryer or stove that runs on 220 volt electricity will have its own circuit.

There are various reasons for the separate circuits. One reason is for the even distribution of electricity. Another reason is so that none of the circuits get overloaded by having too many things plugged in at once that draw more electricity than the wires and receptacles are designed for. Another reason for the separate circuits is for safety. For instance if a stove or dryer catches on fire, their unique circuit can be turned off without having to turn off the electricity for the whole place. All these things are learned when you choose a career as electrician.

There are many types of circuits and items that electricians or an electrical technician wires into the home. Whereas electricians run all the necessary circuits for electricity in the home and sometimes alarm systems, specialists such as telecommunications installers/technicians install and maintain other types of circuitry such as local area networks, telephone lines, TV cable connections, etc…

Some other types of wiring are installed by telecommunications experts also. These include items like room to room intercoms, speaker systems, video monitors and motion detectors. Many newer homes are having these items installed during construction so that the necessary wiring is hidden behind the finished walls. However, there are also electrical specialists that work specifically with installing these types of items long after a home has been built with the hand and power tools of an electrician.

Also, sometimes electricians will install everything from the electrical circuits in a home, to local area networks, alarm systems, speaker systems, etc… during construction without the need for an additional specialist. It usually depends on the electrician’s additional expertise, the homeowner’s desires and any other contracts involved. For instance, sometimes, in order for an alarm company to provide a monthly monitoring service, they require that their company install the alarm system.

The above is just an example of what you will learn in school; http://electriciancareers.org/electrician-courses