Almost every building in the world uses electrical cable, which provides the means through which electricity travels from a power source to a device. Electrical cable and electrical wire are often referred to interchangeably. However, while "wire" has a specific definition as a single conductor carrying current, cable comprises two or more insulated conductors wrapped together. Electric cable has many different classifications.

...
Electrical cable falls into several major types.

Multi-Conductor Cable

Multiconductor (MC) cable contains more than one conductor. MC cable makes up the majority of cable types. All the conductors in multiconductor cable come wrapped in an insulation layer, with another insulation layer covering the outside. Multiconductor cables are easy to use, lending themselves easily to home applications.

Twisted Pairs Cable

Twisted pairs cable contain two conductors, or wires, twisted together. The two conductors do not have individual insulation covers. Their design provides an ideal medium for signal transmission.

Nonmetallic Cable

Nonmetallic (NM) cable thrives in dry, protected areas, such as the insides of walls or the sides of floor joists. NM wire has a couple of subtypes: BX cable, also known as armored cable, has a metal sheath around it, and TECK cable adds another thermoplastic lining over the metal sheath. NM cable consists of three wires: One "hot" wire carries the current and shares duty with one grounding wire and one neutral wire.

Nonmetallic Cable "14-33"

Nonmetallic cable "14-3" has four wires running through it: a ground wire, a neutral wire and two hot wires. Like standard NM cable, NM "14-3" cable works best when used inside of a house.

Large Appliance Cable

Though much larger than NM cable, large appliance cable has a similar design. It usually comes sheathed in black plastic and contains stranded wire—that is, wire made from many small wires twisted together. It is used for 120- and 140-volt circuits.