Statistical Mechanics is a particular bunch of Physics. In which both Macro and Micro system are dealed in respect of the behavior of every constituent but not as a whole. That is why Statistical approach is quite different from Thermodynamic approach. In this course, both Classical and Quantum Statistics are discussed in respect of their most probable distribution, conversion and applications. Here several Thermodynamic Parameters and their characteristics are derived and discussed in Statistical way. Not only that but also the Theory of Specific Heat of solid, Planck's Black Body Radiation Theory and its consequences, Fermi energy state for Free Electron Gas inside metal, Richardson-Dushmann Equation for Thermionic Emission of Electron, Einstein's Theory of Brownian Motion with Langevin's Extension for verification of Avogadro Number along with Gibb's Paradoxical Error and its removal for Entropy Function of gaseous system, ........etc. all are carefully and easily discussed for students realization. Student will be benefited with this high level course when developed at very easy way. I hope the student will collect this course for their easy practice and easy realization about Statistical Mechanics.