A star is primarily a massive, luminous sphere composed mostly of hydrogen and helium.
During the star’s life cycle, hydrogen atoms undergo nuclear fusion in the core, fusing together to form helium. This fusion process releases enormous amounts of energy in the form of light and heat, which is what makes stars shine.
Helium is the second most abundant element in stars after hydrogen, and its formation through fusion is a key step in stellar evolution.
Conclusion:
Thus, a star is a ball of hydrogen and helium, with helium being produced from the fusion of hydrogen in the star’s core.