Non-metallic sheathed cable, also called NM cable or Romex, after the popular brand name, is a flexible electrical cable with a plastic outer coating. That's the non-metallic sheath. Inside the sheath are two or more insulated wires and usually a ground wire. That's for safety.
What is the meaning of Armoured cable?
Steel wire armoured cable, commonly abbreviated as SWA, is a hard-wearing power cable designed for the supply of mains electricity. It is one of a number of armoured electrical cables – which include 11 kV Cable and 33 kV Cable – and is found in underground systems, power networks and cable ducting.
What is metal sheathed wiring?
BX is also known as Armor Clad, or Flexible Metal Conduit cable. BX is sheathed in a flexible metal spiral made either from aluminum or galvanized steel. BX provides all the advantages of NM cable plus some additional benefits. The flexible metal sheathing is easy to install, about as easy as NM cable .