The primary component of a star is hydrogen, making up about 74% of its mass, with helium constituting most of the remainder. Stars generate energy through the process of nuclear fusion, wherein hydrogen nuclei combine to form helium, releasing vast amounts of energy in the form of light and heat. This process is fundamental to the life cycle of a star and influences the formation of elements in the universe, playing a crucial role in the synthesis of heavier elements during stellar nucleosynthesis.