In terms of band Theory, what is the difference between a conductor and an insulator ?

The energy gap between the valence band and conduction band in an insulator is very large, so electrons cannot jump to conduction band and such a substance has very small conductivity. While in a conductor the energy gap between the valence band which is partially filled and conduction band is very small or there is overlapping between them, so electrons can flow easily to conduction band such a substance shows higher conductivity.