Is heat a property of Something? There are some unique properties of things in our world. For example, charge is a property of  mass. Is heat a unique property of something? Can a vacuum/void have a finite amount of heat in it? What about the temperature?
 A: You have come to the right place, and your question will be answered. But, be warned, you may not like the answer.
You can not talk about the heat of anything. No object, system, or molecule can be said to contain this much heat, at all.
A physicist states this as the following: Heat is not a state variable.
What you can talk about is called internal energy of a system. For macroscopic objects, internal energy is defined as the energy due to thermal properties of its internals. Classically, we are inclined to talk about "thermal motion", but internal energy may be just due to fluctuation of quantum states (such as spin) which involves no motion in the classical sense at all. 
Temperature is a measure of internal energy of the system. Note that you can not call temperature a measure of the heat content of the system. Two systems with the same temperature put into thermal contact will not exchange any heat. Now, there is the first place here where heat has been used in the correct context.
Here is the core of the business: Systems can gain or lose internal energy in two ways: Work and heat. When a system does macroscopic work (this is called "useful work" by a lot of authors) it loses internal energy by exporting work. This happens, for instance, when a hot gas expands by pushing on a piston. The temperature of the gas will drop (since it lost internal energy) but it lost the energy as work, and there was no transfer of heat anywhere at all.
The same gas could be put into contact with a cold body, and without doing any macroscopic work (nothing moved) could lose the same amount of internal energy by heat exchange. The temperature still dropped by the same amount, if the work done in the first case is equal to the heat exchanged in the second case.
This is usually expressed as follows:
$dE = d Q + d W$
The two differentials on the right hand side are usually slashed (like $\hbar$ is slahsed) to mean that they are inexact differentials. 
What does that mean? For internal energy, you can look at the initial and final states of a system and say, "the system has lost this much energy". But, looking at the initial and final states of a system, you can not say "the system has lost this much work" or "the system has lost this much heat". That depends not only on the initial and final states of the system, but the path that was taken in getting there; the system could have taken any path.
So, in summary, the thermal part of the energy of a system is called "internal energy".
"Heat" is only defined when the the internal energy exchange between to systems is done via thermal contact. If you wish to use "heat" correctly, always talk about "heat exchange" or "exchanged heat". It is just like a price; which is only well-defined at the moment of the transaction; otherwise it is just money.
"Work" pretty much shares the same property. It is defined when a system does macroscopic work on another. Again, a system does not contain "work". To use it correctly, always talk about "work done by" or "work done on". 
"Temperature" is a measure of internal energy. And temperature is a state variable, and $dT$ is an exact differential. Just because you can say a system has temperature it does not mean it has heat. It has internal energy.
I hope that clears any and all confusion about the subject.
A: I think you have two questions here, namely


*

*What is heat?

*Is it a fundamental property of stuff?


I'll answer both at once.
In modern physics we view heat as an average property of a system containing many particles. Roughly speaking, the heat of box is a measure of microscopic energy transfer between the box and its surroundings.
More precisely, we use the concept of temperature to measure heat. When you've got a large number of different particles it's impractical to keep track of the energy of every one! Taking an overall view, we can mathematically define the temperature as a useful observable quantity.
Hopefully you'll now have an inkling that heat is not a fundamental quantity in physics. Rather it's an emergent phenomenon when you have large systems of particles. It doesn't make sense to ask what the temperature of an electron is! But you can talk about the temperature of your cup of tea, because it contains $10^{25}$ electrons.
CuriousOne is right that you can assign a temperature to the vacuum. In quantum field theory there is a vacuum energy due to virtual particles. If you take a large portion of space, there are many virtual particles. This means you can view the energy as heat!
Finally, a little correction to your question. You shouldn't really say the charge is a property of mass! In fact, there's nothing to stop massless particles being charged. What you mean is that charge is a property of fundamental particles - that is certainly true.
A: The heat as we deal with in everyday life is due to the MOTION of the ingredient particles of that matter which had gained energy. when you give energy the particles motions get faster which means the particles are more energetic and it get's hotter through our sensing.
(then heat as we (possibly) mean here = motion of the particles)
