The Sun sustains itself through a process called nuclear fusion, which occurs in its core. The primary particles involved in this process are protons, which are hydrogen nuclei. The Sun is primarily composed of hydrogen gas, and under the extreme conditions of pressure and temperature in its core, hydrogen nuclei collide and fuse together to form helium nuclei.
The fusion process in the Sun is known as the proton-proton chain reaction. It involves a series of steps that ultimately convert four hydrogen nuclei (protons) into one helium nucleus. During this process, energy is released in the form of gamma rays, which gradually make their way to the Sun's surface and are eventually emitted as light and heat.
To summarize, the Sun "feeds itself" by converting hydrogen nuclei (protons) into helium nuclei through the process of nuclear fusion in its core. This fusion process releases a tremendous amount of energy, which is what powers the Sun and provides heat and light to our solar system.