Conductors are the materials that ensure the easy transfer of heat or thermal energy from one end of the materials to the other end. It permits the electron to flow freely from one end to the other end of the material carrying the heat or charge of the particles.
Insulators, on the other hand, are the poor conductors of heat or thermal energy from one end of the materials to the other end. The electrons in the insulators are not free to move from particle to particle. Therefore the charge or the heat doesn't flow to the different parts of the materials.
Conductors of heat: copper, iron.
Insulators of heat: plastic, rubber.