Energy levels refer to the specific amounts of energy that electrons can have when they are in an atom. These levels are often visualized as distinct "orbits" or "shells" around the nucleus, where electrons reside. Each energy level can hold a certain number of electrons, and the arrangement of these electrons determines the chemical properties of the element. When an electron absorbs energy, it can move to a higher energy level, a process known as excitation. Conversely, when it loses energy, it can drop back down to a lower energy level, often releasing energy in the form of light. This behavior is fundamental to understanding atomic structure and the behavior of elements in the periodic table, such as hydrogen or oxygen.