Thermal energy moves from one object to another through heat energy. Heat energy moves through convection, conduction and radiation. The internal movement of atoms generates energy in matter. As the temperature of matter increases, the internal movement also increases.
Convection occurs when heated particles transfer heat to a different substance. This type of transfer occurs when boiling food in water. Conduction is the transfer of heat through a solid material. Radiation allows heat to transfer through electromagnetic waves.
The transfer of heat energy requires thermal contact between two materials. Transfer of energy is often beneficial. With a gasoline engine, the heat produced by combustion in the cylinder transfers to the metal of the engine and then to the engine coolant. Air passing through the radiator removes the heat buildup from the coolant to prevent overheating.
Thermal insulation is matter that reduces thermal contact. When standing close to a heat source, an individual feels the heat due to convection currents. As he moves away, air serves as an insulator, so he no longer feels the energy transfer from the source. While less than perfect, adding insulation to a home reduces the energy transfer between the air inside the home and that on the outside.