Energy levels refer to the quantized states of energy that particles, atoms, molecules, or systems can possess in quantum mechanics. These discrete energy states correspond to specific values and are characteristic of the system’s potential or kinetic energy. In atomic physics, for instance, electrons in an atom occupy distinct energy levels or orbitals. These levels are depicted by quantum numbers and represent the energy an electron possesses within the atom. Electrons can transition between these energy levels by absorbing or emitting photons, resulting in spectral lines observed in atomic spectra. In molecular and quantum physics, energy levels describe the allowed energy states of molecules or quantum systems. These levels determine the system’s behavior, including electronic, vibrational, or rotational transitions, each associated with specific energy changes.