Valence band: The valence band is another energy band in a solid material that lies below the conduction band. It contains electrons that are tightly bound to their respective atoms.
Band gap: The band gap is the energy difference between the valence and conduction bands. It determines whether a material behaves as an insulator, semiconductor, or conductor.
Fermi level: The Fermi level represents the highest occupied energy state at absolute zero temperature in a solid material. It plays a crucial role in determining electronic behavior and conductivity properties of materials.