Ineed energy from the sun comes from nuclear fusion. what happens during that reaction?

The Sun is a main-sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 620 million metric tons of hydrogen each second. The nuclear binding energy curve.

I hope this helps

This is where fusion in the Sun happens. Every second, 600 million tons of hydrogen are being converted into helium. This reaction releases a tremendous amount of heat and energy. The process of fusion in the Sun is known as the proton-proton chain.