Insulators are materials which do not conduct heat very well and so we can use them to control heat and keep things hot or cold.  Thermos flasks are made from insulating materials.  Conductors are the opposite of insulators.  Heat passes quite easily through them.  We can use conductors to move heat, for example, radiators are made from metal.  That's because metal is a good conductor of heat and so metal radiators warm rooms or cool engines much more quickly than wooden ones would.