The measure of how well an electric current can move through a substance is called conductivity.

Here's a breakdown:

* Conductivity: A material's ability to allow the flow of electric current.

* High Conductivity: Materials with high conductivity allow current to flow easily. Examples include metals like copper and silver.

* Low Conductivity: Materials with low conductivity resist the flow of current. Examples include rubber and glass.

Important Note: The opposite of conductivity is resistivity. Resistivity measures how strongly a material opposes the flow of electric current.