Statistical Thermodynamics is field of physics that applies probability theory to studying thermodynamics. Statistical Thermodynamics is also known as Statistical Mechanics. Statistical Thermodynamics provides a way to relate the microscopic world of atoms and molecules to the world we see around us, providing a molecular level interpretation of thermodynamic quantities.
Statistically entropy is based on the probability of molecular positions and 2nd Law of Thermodynamics’ tendency of entropy to increase results from high entropy configurations being more probable than low entropy ones.
Statistical Thermodynamics shows us why the laws of Thermodynamics work the way they do and connects the microscopic and macroscopic worlds in a way nothing else can do. It shows why entropy tends to increase and how and when it can be decreased. The fact entropy is related to the number of possible configurations that a system may have is why it can be considered a measurement of the degree of disorder in a system since disrobed systems have more possible configurations than ordered systems.