Abstarct: In chromodynamic theory chiral symmetry is also broken and it is not directly possible to enter the quark mass term in lagrangian. This chromodynamic theory baxsed on SU(N_C) group in which N_C represents the number of colors. Different types of quarks are given with the number of N_f. In this thesis we will investigate the non-abelian gauge theory with properties mentioned above. It has been observed that the beta function of the theory depends on N_f and in a certain value the theory contains conformal symmetry which is referred as the conformal window. One of the aims of this thesis is to consider this phase transition. In trying to study these cases we can use holography approach and string theory. AdS/CFT duality helps to study the problems which are strongly coupled with the classical theory of Einstein gravity. For this purpose, a structure of branes is considered as D_3/D_7 model. We study the chiral symmetry breaking property and its relation to parameters such as N and N_f. One of the other aims of the thesis is to study the models beyond the standard particle model. We use the strong four fermion interaction to trigger the chiral symmetry breaking in the theory in Nambu-Jona-Lasinio (NJL) assisted technicolor models. These NJL models provide examples of different dynamics from walking technicolor which can, by tuning, generate a light higgs like σ meson. We compute the vector meson (ρ) and axial vector meson (A) spectrum for a variety of models with techni-quarks in the fundamental representation, enlarging the available parameter space over a previous analysis of walking theories. The large N N=4 gauge theory with quenched N=2 quark matter in the presence of a magnetic field displays chiral symmetry breaking. We study the temperature and chemical potential dependence of this theory using its gravity dual (baxsed on the D3/D7 brane system) and find the orders of transitions and critical points. Finally we use dilaton profile to trigger the chiral symmetry breaking and consider the effects of that on the structure of phase diagram.