Understanding of what energy means I have trying to get my head around the concept of energy to get a satisfying understanding. Energy is a signed scalar quantity that comes into two main forms: kinetic energy (motional energy) and potential energy. All the various forms of energy can be found to be one or a combination of the two forms of energy stated above. Thermal energy, for example, is the internal, microscopic, disorganized kinetic energy of all the atoms/molecules forming the body. Chemical energy is electromagnetic potential energy stored in the chemical bonds, etc.
Kinetic energy is motional, translational, organized energy when a point particle or extended system has when it has a nonzero speed relative to a certain reference frame. Potential energy, on the other hand, is "configuration energy", that is the energy that a system composed of two or more parts has in virtue of the fact that the particles have a mutual relative distance and specific arrangement in space. While the components are in that configuration and at rest, they are experiencing interaction of different nature (electromagnetic, gravitational, etc.) Potential energy does not makes sense for a single entity but also needs to pertain to a system of multiple components.
Feel free to make any corrections please.
My understanding is that saying that a system/body has a certain amount of energy means that it has the ability to change its state (dynamical state or configuration) or the state of another system. Would that be correct? Force causes changes in a system's state while energy differences measure the amount of change in the state of a system...
The kinetic energy of a body can be measured. But as far as PE, we can only measure potential energy differences, correct? Or can we also measure the PE of the system?

 A: I'm not sure exhaustive distinction between kinetic energy and potential energy is possible.
Take the case of compression of a gas, let's say the gas is in a cylinder, a piston can move and compress the gas, the walls of the enclosure are actively temperature managed to always match the temperature of the gas inside.
As the gas is being compressed the piston is doing work on the gas. Conversely, when you allow the gas to expand again the gas is doing work upon the piston.
In effect a gas is elastic, resisting compression. The question is then: should the energy that transfers into and out of the gas be counted as potential energy or kinetic energy?
So while it is the case that distinguishing between kinetic energy and potential energy is useful, I believe it shouldn't be thought of as an absolute distinction.

Potential energy is mathematically defined as an integral of force over distance. As we know, when integrating one must allow for an integration constant.
In the context of physics there are certainly cases where there is a natural choice for a point of zero potential energy. For example: Hooke's law
Obviously the point of zero displacement is the natural choice of the point of zero potential energy.
Still, in mathematical physics all operations evaluate difference of potential energy, hence mathematically the choice of the point of zero potential energy is arbitrary; all that is necessary is that it is treated consistently.
