Wiring: Metal conductors that transmit electricity.
What forms does this take?
EMT (electrical metallic tubing) and PVC (poly-vinyl chloride) conduit, MC (metal clad-a spiral wrap cabling with wire manufactured into it), romex (vinyl sheathed wire commonly found in residential applications).
How do we deal with Aluminum wiring?
Aluminum wiring is still used today in certain applications such as circuits 40 amperes and larger. The main problems encountered with aluminum wiring are in regards to connections to devices such as switches, plugs and light fixtures. The issue is the heat that is emitted through the use of these devices and because aluminum is such a softer metal than the copper that it used today it tends to expand and contract in a way that loosens the connections causing heat and in the worst situation an electrical fire.
If you find that you have aluminum wiring in your house DON’T PANIC! This can be mitigated through a simple process commonly referred to as “pig tailing” at each point of termination (switch, plug, fixture). Don’t delay, however, as CPSC research shows that "homes wired with aluminum wire manufactured before 1972 are 55 times more likely to have one or more connections reach "Fire Hazard Conditions" than are homes wired with copper.
Of course, if given the option, it is always better to install new copper romex if it is not a tremendous disturbance.