This lecture covers the principles of statistical mechanics, focusing on the Boltzmann, Bose-Einstein, and Fermi-Dirac statistics. It begins with an introduction to Boltzmann statistics, explaining how particles in a gas can occupy various energy states and how temperature influences their distribution. The instructor discusses the probability of occupation for different energy levels and the significance of energy conservation in closed systems. The lecture then transitions to Bose-Einstein statistics, particularly for photons, highlighting the differences in occupancy compared to classical statistics. The concept of indistinguishable particles and the implications for photon behavior in lasers are explored. Finally, Fermi-Dirac statistics are introduced, emphasizing the exclusion principle for fermions and the behavior of electrons in energy states. The lecture concludes with a comparison of the three statistical distributions and their applications in quantum science, providing a comprehensive understanding of how these statistical models describe the behavior of particles in various physical systems.