Statistical physics is the branch of physics that uses methods of probability theory and statistics to solve problems involving large populations (for example large number of atoms or molecules). Its main purpose is to uncover the aggregate properties of systems (for example, thermodynamic relationships) in terms of microscopic laws governing the behavior of its components (for example, the laws of motion of the molecules).
Because statistical physics is eminently mathematical, it can describe complex systems in a wide variety of fields with an inherently stochastic nature. Therefore, it has many applications in fields as diverse physics, biology, chemistry, neurology, and even the social sciences.