Coaxial Cabling

The cable that connects to your cable TV box is coaxial. That means that in its center--its axis--it has multiple strands of copper and is protected, usually, by an outer sheath of braided aluminum. This sheath reduces signal interference and allows the cable to go a long distance without interference becoming an issue

RG-6 Coaxial

RG-6 is a type of coaxial cable. The quality of the cable, determined by the potentially exotic materials use in its construction, has no actual bearing on the RG label. RG is an obsolete military specification that stood for "radio grade."

What RG-6 Means

These days, RG-6 just means that the cable uses 18 AWG copper wires. AWG stands for American Wire Gauge and is a measurement of an individual wire's diameter when looked at from a cross-section perspective.

18 AWG Defined

The higher the AWG number, the narrower the diameter of the wire. An 18 AWG wire is about the thickness of a strand of angel hair pasta. In an 18 AWG RG-6 cable, these wires will be bunched up inside the sheath.

Other AWG Factors

The AWG number also determines how much electrical current a wire can handle, but keep in mind that a cable with a higher RG number is not necessarily better, and a generic coaxial cable may be just fine for your purposes.

Source:

RG-6 overview

AWG chart