The paper reviews the theoretical basis and applications of QCD sum rules for hadronic physics. It discusses the general procedure, including correlation functions, operator product expansion, and the role of nonperturbative effects. The calculation of Wilson coefficients for perturbative and nonperturbative operators is detailed, along with their applications to two-point functions of hadrons, including mesons, baryons, and quark systems. The method uses moments and Borel transforms to enhance the dominance of the lowest lying resonance. The paper also covers three-point functions, such as decay processes and form factors, and discusses the validity of the operator product expansion in QCD. It highlights the importance of nonperturbative effects, such as vacuum expectation values of quark and gluon condensates, and their impact on hadron masses and couplings. The paper concludes with a discussion of the limitations of the method and its applications to various hadronic systems, including charmonium, upsilon, light quark mesons, and baryons. The results are compared with other approaches, such as lattice calculations and potential models, and the paper emphasizes the role of chiral symmetry and duality in understanding hadronic properties.The paper reviews the theoretical basis and applications of QCD sum rules for hadronic physics. It discusses the general procedure, including correlation functions, operator product expansion, and the role of nonperturbative effects. The calculation of Wilson coefficients for perturbative and nonperturbative operators is detailed, along with their applications to two-point functions of hadrons, including mesons, baryons, and quark systems. The method uses moments and Borel transforms to enhance the dominance of the lowest lying resonance. The paper also covers three-point functions, such as decay processes and form factors, and discusses the validity of the operator product expansion in QCD. It highlights the importance of nonperturbative effects, such as vacuum expectation values of quark and gluon condensates, and their impact on hadron masses and couplings. The paper concludes with a discussion of the limitations of the method and its applications to various hadronic systems, including charmonium, upsilon, light quark mesons, and baryons. The results are compared with other approaches, such as lattice calculations and potential models, and the paper emphasizes the role of chiral symmetry and duality in understanding hadronic properties.