Welding cable is the electrical conductor for the welding current. It consists of a series of fine copper strands wrapped inside a non-conductive, durable jacket (typically some type of synthetic or natural rubber of various colors). The fine copper strands give welding cable more flexibility than other types of electrical conductors and the insulating jacket is designed to hold up to repeated movement over rough surfaces. As the current level increases (measured in amperage or amps), the diameter of the welding cable and resulting cross sectional area of the copper stranding needs to increase. The concept is similar to the flow of water through a hose. A larger diameter hose is needed in order to carry a greater volume of water. You use a smaller hose to water your garden, while the fire department uses a much larger hose to fight fires.