Among the electronic structure methods, Density Functional Theory (DFT) is the most widely used. Instead of solving for the full N-electron wave function n, DFT predicts the electronic density (r), reducing the problem to three spatial dimensions. This impressive dimensionality reduction is achieved by introducing functionals that curb the electronic energy to hold a specific dependence on (r). These functionals, ranging from simple expressions to complex parameterized forms, are imposed ad hoc, meaning DFT is not strictly an ab initio method. To describe excited electronic states, we use Time-Dependent Density Functional Theory (TDDFT). It extends DFT to capture a molecule's response to time-dependent external fields, allowing the calculation of excitation energies and absorption spectra with a balance of accuracy and computational cost.