Thermodynamics is the branch of physical science concerned with the relationship between heat, work, temperature, and energy. It governs the transfer and transformation of energy within physical systems, establishing fundamental laws that dictate the efficiency and feasibility of processes. The First Law states that energy cannot be created or destroyed, only converted from one form to another. Complementing this is the Second Law, which introduces the concept of entropy, defining the directionality of natural processes by stating that the total entropy of an isolated system can only increase over time. These principles are critical for understanding everything from chemical reactions and mechanical engines to biological metabolic processes, forming the basis for calculating energy yields and system efficiencies.