Well, the energy comes from the proton-proton chain which collides two protons, forming a deuterium core, a positron and a neutrino. The positron almost instantly annihilates with an electron, creating a gamma ray of energy. The deuterium core then collides with a second proton, forming helium-3 and releasing another gamma ray in the process.
How the actual sunlight forms, I don't know tho. It has something to do with the neutrino carrying energy to the protosphere, but what happens there, dunno.
I would hope the whole thing is a joke in general.
"The sun gives us light when it's 'already' bright" is where the real logic breaks down. "I don't need <thing> because I already have <benefit from thing>" is circular logic.
So of course we wouldn't have sunlight at night without the sun. but we also wouldn't have sunlight at night without the moon.
Whether we want to call it "more useful" than the sun... it is just as useful as the sun at night. We need both of them for the system to work. I was just trying to snarkily emphasize that we shouldn't downplay the moon because it is "just" reflecting sunlight.