It is not always possible to obtain rigorous analytical solutions to diffraction problems because of geometrical and physical complexity of most scattering surfaces. Wiener-Hopf (WH) method is applicable to plane discontinuities like two or three –part plane problems, open structures like an infinite set of parallel half-planes and closed structures like parallel plate waveguide. The main purpose of this study is to give an overview of the Wiener-Hopf technique, related factorization and decomposition methods. In order to outline the theory, five types of Wiener-Hopf geometries and solution methods for the diffraction of electromagnetic waves from these geometries were investigated.