In this report, I have discussed the theoretical background of density functional theory and the solvation model. We extensively describe Born-Oppenheimer approximation, Hartree-Fock and Thomas-Fermi theory, Hohenberg-Kohn theorems, Kohn-sham approach, Exchangecorrelation approximation and self-consistent method. Furthermore, we have discussed Basisset and solvation model, especially the polarisable continuum model. I hope that this brief note will be very helpful to understand DFT and solvation model in a limited and short time.