In everday use, energy seems to be a kind of substance found in food, coal, and batteries, and which can be transmitted over electrical wires. However, energy is not a substance but rather a quantity that is abstracted from the configuration and motion of a physical system without actually being a part of any concrete physical thing. In our imagination, energy can appear to flow like a substance because it is conserved and thus if it goes down somewhere it generally rises somewhere nearby.
Of course, the everyday use of energy does not refer to a strictly conserved quantity. Energy gets used up. Food is consumed. A battery runs out and is thrown away. Not all energy can drive machines and living things. The imaginary substance called energy is more closely related to the physics concept of the free energy which is a function that is used to calculate the energy in a system that is available for useful work. The free energy, hoewever, is relative to the surroundings. Machines are less effient if the surrounding temperature goes up, for example.