"Sunshine" and "moonlight"

That's several thoughts that have come to mind, so here's several answers.

• The sun shines. The moon shines too, albeit with reflected light.

• Sunshine and sunlight are synonymous, but still subtly different. Sunshine generally refers to the illumination outside on a sunny day, particularly the visible light, and has strong positive emotional connotations. "He's a regular ray of sunshine" is a way of describing an infectiously happy person. Sunlight in contrast is more emotionally neutral, and refers to any light (or other EM radiation for that matter) coming from the sun.

• Moonlight and moonshine are a bit more different. Moonlight is loaded with all sorts of emotional baggage: romance, mystery and madness to name but three. Moonshine on the other hand is rarely used for the light from the moon, mostly in poetic imagery. More usually it refers to (illegal) backwoods whisky!

To expand on that last bit, since Etymonline is rather terse: objects and landscapes tend to look rather different and strange when viewed by moonlight, so moonlight itself has connotations of unreality and illusion. There are any number of faerie stories involving gates that can only be found when the light of the full moon falls on them, fabulous treasures that turn out to be just leaves and moss in the morning light, and so on. Moonshine whisky in that sense is pushing the notion that the illicit hooch is only as real (and hence taxable) as something seen by moonlight, i.e. not really there at all. Likewise the things you'll see if you drink too much of it!

I think "moon shine" would be used except that it conflicts with moonshine which is a powerful homemade whiskey. Even if the meaning is fairly evident by the context, nobody wants to use words in poetry that might make you think of something completely unlike what you intended.

I've always heard "the moon beams" as an equivalent to "the sun shines" for the moon.