On the literally true side (from what I understand): The eye doesn't "see". It feeds information, measurements, shades, etc., back to the brain and the brain manufactures a picture based on that information.
A reflection of the moon in water: Metaphorical. You and I are like a reflection of the moon in water. How so? The reflection of the moon in a lake makes the moon appear to be there in the water, but of course it isn't, it's merely a reflection. What makes it appear though is a series of "conditions". The Buddhists call this "conditioned existence", also "emptiness". If there are clouds, or the angle of the moon isn't right, or the phase doesn't allow for a reflection, etc., etc., the moon won't appear in the water of the lake. The "conditions" weren't right.
You and I, the actual moon, mountains, trees, everything you see, feel, taste, think, and so on are like that reflection in that we only appear, exist, due to certain conditions. When those conditions change we no longer appear, exist. If the conditions that made the entire universe appear hadn't existed, there wouldn't be a universe. And if you believe in God, you can factor God into that.
So, we are a reflection in that we exist due to conditions. We aren't the solid phenomenon that we think we are. We don't exist on our on side only. We exist due to a series of other factors, or conditions. No different then the moons reflection in water.
Why might that understanding be important in the relief from suffering that is the point of Buddhism? That's up to you to figure out, or not, as you wish.
