A conductor is a material which electricity, heat or sound can flow through. Most metals, like iron and copper, are electrical conductors. These metals are used to make wires. Plasma[disambiguation needed] is an excellent conductor of electricity and more uses for this property are being discovered every day.
Some materials are semiconductors. This means that electricity can flow through them, but not very well.
Some materials are resistors. This means that they make it very hard for electricity to flow through them.
Some materials when really cold, are superconductors. They offer no resistance at all to the flow of electricity.