Which kind of process supplies the energy for the stars?

The process that supplies the energy for the stars is nuclear fusion. Nuclear fusion is a process in which atomic nuclei combine to form a heavier nucleus, releasing a large amount of energy in the process. In stars, the fusion of hydrogen atoms into helium is the primary source of energy. Under the intense heat and pressure of a star's core, hydrogen atoms are fused together to form helium, releasing a tremendous amount of energy in the form of light and heat. This process is what allows stars to shine and provides the energy necessary to sustain life on Earth.