An electrical conductor is a material that allows electric currents (flow of electric charges) to pass through it. All metals are electrical conductors.
An electrical conductor has lots of charges that are free to move. In a metal, the charges that are free to move are electrons. The electric current through the metal is the flow of these free electrons.
An electrical insulator is a material that doesn’t allow electric currents (flow of electric charges) to pass through it. Plastic and glass are electrical insulators.
An electrical insulator has no free electrons. No charges are free to move and carry a current.
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