Which statement best describes an electrical conductor?

A conductor is defined as a material that permits the flow of electric current due to the presence of free-moving charge carriers, typically electrons. This characteristic allows electric current to easily pass through the conductor, making it essential in electrical circuits and applications.

In contrast, the other options describe different concepts. The first choice refers to insulators, which are materials that impede the flow of electric current, preventing it from passing through. The third option mentions a device related to the measurement of voltage, which does not define a material's conductive properties. Lastly, while there are chemicals that can enhance conductivity, they do not represent the fundamental property of a conductor itself, but rather pertain to ways to improve or modify material conductivity. Hence, the second choice correctly identifies an electrical conductor's primary role.