Abstarct: The potentioal of a quark and anti-quark has been computed using holography, recently. Considering the path of a quark in space time and Wilson loop, one finds that it equals to the expectation value of the Wilson loop. Therefore, in strangly-coupled supersymmetric Yang Mills theory with large N_C the partion function of string equals to the classical action of the string. In this thesis, we state that in plasma, the real part of the potential corresponds to the free energy of heavy quark and antiquark . It is shown that at low energy, the free energy and bound energy do not depend on the temperatur. We have also computed the quark and anti-quark distance. The bound energy of quarkonium is calculated with subtraction of energy of two intracting quarks from two independent quarks. We have plotted the free energy and the bound energy as a function of quark anti-quark distance. Also, entropy and internal energy of quarkonioum and free energy of quark in terms of the temperature has been calculated. These quantities have been studied in N=4 SYM and in non conformal theories. Considaring R^4corrections, we have studied finite copling correction. It is shown that with increasing the copling, the free energy decreases.