Part-1: Good conductors
The substances which allow the heat to pass through them easily are good conductors of heat.
Mercury, copper, silver, iron.
The above mentioned substances allow the heat to pass through them easily.
Part-2: Bad conductors
The substances which do not allow the heat to pass through them easily are bad conductors of heat
Wood, air, saw dust, plastic, wool, cardboard.
The above mentioned substances do not allow the heat to pass through them easily.