The present tutorial 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 tutorial also presents the relativistic model, consisting of a Lorentz scalar potential a vector potential. In compliance with the tradition, the scalar potential and the vector potential are treated in the same fashion as the central potential in the Schrödinger equation.