There are three main types of wire in use in homes today, each with its own distinct properties. The first major type is known as Romex and this is a single sheathed plastic insulated wire that is used for running cables throughout walls, ceilings, and floors. This type is not flame retardant so it cannot be used around places where things may get hot enough to cause a fire hazard. It is available in various thicknesses denoted by the number of wires inside the cable. The thinner stuff can handle up to 100 amps at 120 volts while thicker cable can manage 150 amps at the same voltage level.
The second most common type is known as Copper which comes in either rigid or flexible form. Copper is not only a great conductor of electricity, but it is also an excellent conductor of heat which makes it perfect for use in things like ovens and space heaters. It is also possible to find this type of wire with a non-metallic coating on the outside, making it easier to install inside walls without having to make a hole.