When regular ordinary wire is used to carry high frequency currents the high frequency currents radiate off of the wire as radio waves.  Coaxial cable prevents radio wave and power loss by using a conductor enclosed in another conductor.  Both the central wire and the metallic tubular shield are conductors.  AC or alternating current will travel through both of these conductors in opposite directions and reverse directions millions to billions of times per second.

The dimensions and spacing of the two conductors must be uniform throughout the length of the coaxial cable. Uneven spacing between the two conductors contained within the coaxial cable will reflect radio frequency power back toward the source, which causes a condition called standing waves that reduces the amount of power reaching the destination end of the cable. A semi-rigid tubular plastic dielectric insulator keeps the metallic shield (also a conductor) at a uniform distance from the central conductor.

The final component of coaxial cable is the insulating jacket, which can be made from many different types of materials. The most common choice for the plastic insulating jacket is PVC. Outdoor coaxial cables may require additional ultraviolet light and oxidation protection. For internal coaxial connections the insulating jacket can even be omitted altogether.  And the final bit of coaxial cable that completes a connection from point A to point B is an RF connector.