Electronic structure is a branch of condensed matter physics and materials science that focuses on the study of the arrangement and behavior of electrons in atoms, molecules, and solids. This field involves theoretical and computational methods to understand the electronic properties of materials, such as their energy levels, band structures, and bonding interactions. Electronic structure calculations can provide valuable insights into the fundamental properties of materials, as well as guide the development of new materials with specific electronic properties for applications in electronics, photonics, and energy storage.