Basically, the P-P chain turns 4 protons into: 1 neutrino, 1 gamma ray, 1 positron, 1 helium nucleus.
A gamma ray = energy.
The chain converts hydrogen into helium and makes energy.
This is all occurring through fusion reactions where 2 protons basically smash into each other. But, it could also be e.g. a proton smashing with a deuterium nucleus. Or, other nuclei smashing together to make something else.
Hope this helps!
