Tom, it doesn't help for you to merely quote the Wiki when the question being asked is " What does this line from the wiki mean?" Especially if the line you quote was actually already quoted by the other guy, which means he saw it already and it didn't help the first time he read it. It probably won't help the second time either, especially removed from the surrounding context.
So I will tell you what I nderstand Rabinoz's question to be. Maybe I'm wrong, in which case I apologize, but I would like an answer myself, so nothing lost. Here it is: How can a shadow illuminate anything? That's not what shadows do, illuminate. They block illumination.
Here's the line again, with my emphasis addd to bring attention to the part we're asking about: "When one observes the phases of the moon he sees the moon's day and night, a shadow from the sun illuminating half of the spherical moon at any one time." Clearly states that a shadow is illuminating the moon, we/I just wonder what that means. I think it might just be a typo, but I would lke to know for sure.