What gives moon its light?

Because at night it functions as a mirror for the sun. It's like this:

You -------> (watch in this direction) ----> Moon (mirroring the sunlight in your eye)

-------------------------------------- ..................^

Earth (blocks the sun) ............................../

.............................................................../

............................................................/

........................................................./

....................................................../

..................................................Sun

(forget about the dots, that's just to position the lines because I can't type spaces in this drawing)