The equation to measure thermal conductivity, or heat transfer, is created by measuring the heat multiplied by the distance of the heating material divided by the area multiplied by the temperature gradient. The equation looks like this:
Thermal Conductivity = heat --- distance / (area --- temperature gradient)
To get an accurate reading of heat transfer, neither the item nor the heating material can move. Movement causes friction, which skews the results -- because friction can speed up the transfer of heat. Friction causes molecules to move faster, thus creating more heat. The thermal conductivity coefficient is meant to measure the transfer of heat while everything else remains constant -- thus, the heated material and the item must remain still.
When heat flows into an item, it begins to decrease because the energy is moving from a very energetic molecular item (the hot material) to a less energetic molecular item (the cold item). The energy is transferred to the cold item, making it warmer, which causes its molecules to move more rapidly -- and the hot material then loses heat because its energy is being put into the cold item; its molecules begin to move slower as a result.
The thermal conductivity coefficient is useful in a lot of everyday scenarios -- from warming a baby bottle to understanding heat loss through the walls of a house to save on energy bills. Another use of heat transfer that most people do not even know they are doing is testing the temperature of a bath with their elbow or fingers. If the water is too hot, that means the molecules are moving too quickly and the heat transfers to our skin and burns. If it is just right, then the molecules are moving quickly enough to be warm, but not fast enough to burn us. While we do not use the coefficient to measure this, we could easily do so and see that a perfect bathtub would transfer the water's heat to our skin and stop heating in about 5 seconds.