So the moon’s dark portion is being indirectly lit by sunlight bouncing off the earth. Pretty neat. This must not be too terribly rare because I think I’ve seen it before.
No, not so rare, except for the position of Venus, but still difficult to capture with a camera.
Every new moon shows it to one degree or another, depending on the cloud cover of the moon-facing hemisphere ( cloudier = brighter ). The remarkable thing about this photo, and most of these types of shots, is the amazing photosensitivity and resolution of modern cameras.