In this paper, a theoretical approach comprising the nonequilibrium Green's function method for electronic transport and the Landau-Khalatnikov equation for electric polarization dynamics is presented to describe polarization-dependent tunneling electroresistance (TER) in ferroelectric tunnel junctions. Using appropriate contact, interface, and ferroelectric parameters, the measured current-voltage characteristic curves in both inorganic (Co=BaTiO 3 =La 0.67 Sr 0.33 MnO 3 ) and organic (Au=PVDF=W) ferroelectric tunnel junctions can be well described by the proposed approach. Furthermore, under this theoretical framework, the controversy of opposite TER signs observed experimentally by different groups in Co=BaTiO 3 =La 0.67 Sr 0.33 MnO 3 systems is addressed by considering the interface termination effects using the effective contact ratio defined through the effective screening length and dielectric response at the metal-ferroelectric interfaces. Finally, our approach is extended to investigate the role of a CoO x buffer layer at the Co=BaTiO 3 interface in a ferroelectric tunnel memristor. It is shown that in order to have a significant memristor behavior not only the interface oxygen vacancies but also the CoO x layer thickness may vary with the applied bias.