Fission and fusion are both processes which create energy by atomic nuclei either being broken apart (fission) or combined together (fusion). The Sun, like all stars, only undergoes fusion reactions. In this process, 4 hydrogen nuclei are mashed together in the interior of the Sun to make 2 helium nuclei; in the process energy is released. As the store of hydrogen is used up (over billions of years) the Sun will begin to fuse the helium, as well as other atomic nuclei to continue to create energy.
Within our own Solar System, we have examples of bodies that both emit and reflect light. The Moon is illuminated only by reflected sunlight. In contrast, the turbulent gas giant planet Jupiter emits radiation.