The present lecture course is dedicated to the study of the nonrelativistic Schrödinger equation and its application in the distorted-wave Born approximation (DWBA) and coupled-channels (CC) calculations. The course also presents a relativistic model consisting of a Lorentz scalar potential (Us), and a vector potential (Uv). These potentials are treated in the same fashion as the central potential in the Schrödinger equation. Considered are examples when the Dirac equation is reduced to a Schrödinger-like one with constraints, including only the upper component of the Dirac wave function. Such a transformation is often defined as the “Schrödinger-equivalent potential”, although some researchers prefer to term it the Dirac-equation-based (DEB) optical potential.