Abstract: First, we review the hadrons predicted by the group theory and discuss the reliability of the the QCD Lagrangian. Then, introducing some non-perturbative approaches, we briefly review the QCD sum rules formalism as one of the most powerful and applicable non-perturbative methods to hadron physics. We calculate the mass and decay constants of some light and heavy baryons and mesons both in the vacuum and finite temperature, in the framework of the QCD sum rules. We also calculate the coupling constants as well as form factors characterizing the electromagnetic, weak and strong transitions of hadrons in light cone QCD sum rules. Using the obtained results for the form factors and coupling constants, we evaluate some related observables such as charges, electromagnetic multi-poles, decay rates, branching ratios, various polarization asymmetries, etc. We compare our results on the quantities under consideration with predictions of some other non-perturbative approaches, Lattice QCD as well as existing experimental data.