what does good conductor of heat and electricity mean?
Good conductor of heat, like copper, quickly lets heat flow in it to equalize any temperature difference. So if you put one end of a copper bar in a fire, the other end would quickly get hot. Copper and aluminum are usually used for heat sinks for this reason. Good conductor of electricity, like copper again, means that electric current can flow through it with a small voltage drop. That is why copper is used in electric wires. .
