Quark Model, Nonperturbative Wave Functions, the QCD Sum Rules and Instantons

The main subject of these lectures is the Nonperturbative Wave Functions. We describe some nonperturbative methods (like QCD sum rules, dispersion relations, duality etc) in order to study this object. We also consider some applications of the obtained results, such as form factors, inclusive amplitudes and diffractive electroproduction. Finally, we discuss the instanton liquid model which may help us to understand the success of the constituent quark model.