An "energy layer" refers to a specific region in a system where energy is stored or transferred. In physics, this concept is often used to describe the arrangement of electrons in an atom, where each layer corresponds to a different energy level. These layers help explain how atoms interact and bond with one another. In the context of geology, energy layers can also refer to different strata within the Earth's crust that contain various forms of energy resources, such as oil, natural gas, or coal. Understanding these layers is crucial for energy exploration and extraction.