Gibbs free energy, denoted as G, is a crucial thermodynamic parameter that combines enthalpy (H) and entropy (S) to predict the spontaneity of a chemical reaction at constant temperature and pressure. Represented by the equation G = H – TS, where G is the Gibbs free energy, H is enthalpy, T is temperature, and S is entropy, a negative change in Gibbs free energy (ΔG) indicates a spontaneous process. This concept plays a fundamental role in chemistry and biology, guiding the understanding of reaction feasibility and direction. By assessing ΔG, scientists can predict whether a reaction will proceed without external influence and gain insights into energy transformations during physical and chemical processes.