First let us talk a little bit about heat transfers. Heat can transfer from one object to another and it does so in three main ways; radiant, conduction, and convection.
Radiant heat transfer is when invisible electromagnetic waves and visible light bring the energy from one hot surface to another, for example when you put your hand above a candle you feel the heat without touching the candle because of radiant heat transfer.
Conduction heat transfer is the transfer of heat through a material. Conduction is caused when the molecules in one part of the material heat up and start to move faster as they heat up, they then transfer that heat to the molecules next to them and this gets passed on until the heat is transferred throughout the material. An example of this is when you put a metal fork in a bowl of soup and after a while the who fork is hot due to the transfer of the heat in the hot soup to the fork.
Convection heat transfer is when movement of liquids or gases transfers heat. An example of this is when the heat from a stove top warms up a pot of water and the heat is transferred through the water which if hot enough will cause it to boil or simmer.
Image from: http://www.spectrose.com/modes-of-heat-transfer-conduction-convection-radiation.html