Density Functional Theory (DFT) is a computational quantum mechanical modeling method used to investigate the electronic structure of many-body systems, particularly atoms, molecules, and solids. It simplifies the complex interactions of electrons by focusing on their density rather than their individual wave functions, making calculations more efficient and feasible for larger systems. DFT is widely applied in fields such as chemistry, physics, and materials science to predict properties like molecular geometry, reaction energies, and electronic behavior. By using functionals, which are mathematical expressions of electron density, DFT provides valuable insights into the stability and reactivity of various substances.