Why can I see the whole moon during various non-full-moon phases? Here's an image that describes the phenomenon I'm asking about.  The very thin sliver to the left is of course the surface of the moon as lighted by the sun.  But the rest of the moon is also faintly lighted -- by what?

I'm guessing that some amount of "earthshine" -- sunlight reflected from the earth -- is the culprit here, but I've found no authoritative confirmation online. It would be great to have a link to a source that explains what's really going on.
The dark parts of the Moon are partially illuminated by &quot;Earthshine&quot;. That is sunlight which is reflected from Earth to the Moon. Just like the ground on Earth is lit up a bit by the Moon at night, so is the ground on the Moon lit up a bit by the Earth in the lunar night. And even more so because Earth is much larger in the lunar sky, than is the Moon in our sky. And the surface of Earth is actually more reflective per area unit than is the surface of the Moon.