The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another. This principle emphasizes the conservation of energy in any process, meaning the total energy in a closed system remains constant. For example, when fuel burns, its chemical energy is converted into heat and light energy. In practical terms, this law is crucial in various fields, including physics, engineering, and chemistry. It helps explain how engines work, how heat is transferred, and how energy flows in ecosystems. Understanding this law is fundamental to studying energy systems and their efficiencies.