This self-contained text provides a sufficient theoretical basis to understand Green¿s function method, which is used to solve initial and boundary value problems involving linear ODEs and PDEs. It presents a variety of approaches, including classical and general variations of parameters, Wronskian method, Bernoulli¿s separation method, integral transform method, method of images, conformal mapping method, and interpolation method. The text also covers applications of Green¿s functions and contains numerous examples and exercises from diverse areas of mathematics, applied science, and engineering.