Band structure is a concept in condensed matter physics that describes the arrangement of the energy levels of electrons in a solid material. When multiple atoms come together to form a crystal lattice, the energy levels of their electrons merge and form energy bands. These bands can be either filled with electrons or empty, and the arrangement of these bands determines the electrical and optical properties of the material. The band structure of a material can be studied and analyzed using techniques such as band structure calculations, which use mathematical models to predict the behavior of electrons in the material. Understanding the band structure of a material is crucial for designing and engineering new materials with specific desired properties, such as semiconductors or superconductors.