Heat is a defined amount of energy within an object or mass. No "heat" would represent absolute zero- that is absolutely no energy contained within the object- Absolute zero is regarded as an unattainable limit- like the speed of light. You might get very close to it. but, you probably will never attain it. As the temperature of an object increases 9as described from a starting point, such as "absolute zero" it is said to contain a given amount of "Energy"- that is, it has enough energy to cause a given amount of work. As work is derived from the heat energy within the object the heat level will obviously decrease. Imagine a steam engine powered by a boiler that is heated by a very hot iron ingot. Steam absorbs the heat from the ingot as the engine 'works" absorbing the energy that had been stored as heat within the ingot. eventually, the engine will have absorbed as much energy as the ingot had been able to provide. yet, the ingot is still hot, it is just below the heat level that can boil water to make the steam. That energy can then be used to pwoer, as an example, a small heat engine like a steriling engine. Again, the little engine absorbs the heat energy until it can no longer work. yet, since the ingot is still above absolute zero in temperature, it could, theoretically, still eprform work if there were an engine device capable of absorbing the remaining heat and converting it to work. The final temeprature of the ingot, of course, is absolute zero, at which it no longer will contain any heat capable of work- not even allowing atoms to vibrate, or electrons to orbit a nucleus. It would no longer be capable of performing work- all of its "energy" would have been absorbed.