The valence band is a crucial concept in solid-state physics and materials science. It refers to the highest range of energy levels that electrons can occupy in a solid at absolute zero temperature. Electrons in the valence band are involved in forming chemical bonds and determining the electrical properties of materials. In semiconductors, the valence band is separated from the conduction band by a band gap. When energy is supplied, such as through heat or light, electrons can jump from the valence band to the conduction band, allowing the material to conduct electricity. This behavior is essential for devices like transistors and diodes.