Physicists, especially those looking into quantum mechanics, have come to understand the universe as a manifestation of energy.It is a marvelous thing to be able to grasp just an inkling of the grandeur of the creation that surrounds us. The universe, includes all the heavenly bodies (stars, galaxies, planets, sun, moon and much more), and everything we could ever think of with our limited thoughts - including ourselves.
We also are part of this universe, not separate from it. Therefore, being a part of this unimaginably vast universe, we are also a manifestation of energy. According to science, energy can manifest in many forms and in many states. The currently understood states of matter are solid, liquid, gas and plasma. In general, we are basically aware of only the physical (material) manifestations of energy which includes physical bodies and thought.
It is a complex matter to try to understand what energy is in essence. Definitions and explanations have been invented so that we can talk about energy, but in essence no one really understands what energy is. There are various explanations and from the world of quantum physics we get a 'feel' for energy as something that in its basest form has a vibratory nature. That is to say that the basic way that energy manifests initially is through various sorts of vibrations or frequencies. Thus light, for example, is a vibration at a certain frequency, and when the frequency of vibration of photon energy changes, then the colour of light changes. When the vibration rate reaches the x-ray frequencies then the manifestation of energy behaves as x-rays, etc.
In the same way we can say that energy vibrates in specific ways to manifest every physical phenomenon of which we can be aware. This includes the entire human body. In fact one can think of the 5 senses as being devices that interpret the various vibrations of the universe so that we can understand them at our physical level of manifestation. We can consider our eyes as sensors for receiving light frequency vibrations. The eyes 'interpret' this energy so that we can become aware of the various physical manifestations that reflect the light. Our sense of touch is an interpreter of energy also. Touch interprets heat energy when we are in the warm sunshine, or the heat on the stove top. Also our touch interprets that our hand does not pass through a wall when we push against it. But our touch sense fails to tell us that the 'solid' wall is really mostly empty space composed of atomic nuclei and electrons sparsely spaced. Our hand is also of like nature.
But for a reason it cannot pass through the wall. Similarly, the rest of our senses interpret other areas of energy manifestation so that we can experience the "physical" universe/world.
Oh, by the way, those 5 senses which are the interpreters of the manifestations of energy are in fact themselves made of manifestations of energy. So in essence we have one level of manifestations of energy interpreting other levels of manifestations of energy. And to add to this complexity, we have another manifestation, the brain/mind, which further interprets (or does it?) what our senses bring to it.
So what are we in essence? A very difficult question indeed. But by logical deduction it would seem that we are in essence Energy Beings, and since no one really knows what energy is, then the human being remains a mystery to us. We are a mystery to ourselves. Is it a wonder that we have problems, and various religions, mythologies and superstitions which attempt to provide us with some understanding or at least try to pacify us?
Science also tells us that energy can neither be created nor destroyed. In other words, energy comes closest to what we understand to be eternal. A logical extension of this discussion would then be that we are Energy Beings and Eternal Beings having a human experience. Or one could say that we are "Spiritual beings having a human experience". (Define the word 'Spiritual' as you wish).