These two types of electrical cable are both manufactured as different awg sizes of Romex® cable. Romex® NMB is a trademark name created by Southwire Company similar to the fact that a "Kleenex" is a trade name instead of a tissue.

The term "Romex®" is used to describe a multi THHN wire electrical cable. Romex® cables come with or without a bare ground wire but since almost all customers require one we only stock our cables with the ground wire.

Romex® 14/2 refers to the awg (American Wire Gauge) size first and the number of THHN wires second. In this case you have two 14 awg wires, which come solid instead of stranded, and a bare copper ground wire. Just like the picture below. This cable also comes in a Romex® 14/3 which is three THHN wires and a bare copper ground wire.

You can probably figure out on your own that a Romex 6/3 has three 6 awg wires and a bare copper ground. However, any Romex® cable manufactured bigger than 10 awg is made stranded instead of solid and also black insulation. That makes each 6 awg wire stranded except the solid ground wire.

Each gauge size of electrical wire is used to supply different amount of power. Your electrician can set you up with the right size Romex® cable based on the National Electric Code.

Romex® Wire	UFB Underground Cable