Here's a simplified breakdown of the process:

1. Proton-proton chain: Two hydrogen nuclei (protons) collide and fuse to form deuterium (a heavy isotope of hydrogen). This releases a positron (antimatter electron) and a neutrino.

2. Deuterium fusion: The deuterium nucleus then collides with another proton, forming helium-3 (an isotope of helium). This releases a gamma ray (high-energy photon).

3. Helium-3 fusion: Two helium-3 nuclei collide and fuse, forming a helium-4 nucleus (regular helium) and releasing two protons.

This process releases a tremendous amount of energy, which is what powers the Sun and provides light and heat to Earth.

While hydrogen fusion is the dominant process, the Sun also undergoes other fusion reactions, like those involving carbon, nitrogen, and oxygen. These reactions occur at higher temperatures and pressures found in the Sun's core and are part of the CNO cycle.