What does earthshine mean?
The photo of the Moon shows a lighted crescent shape plus what looks like a shadow that covers the dark part of the Moon that faces Earth. The shadow area of the Moon is visible because of the faint light from the Sun that is reflected from the Earth, and then onto the dark part of the moon.
Since you only see objects that send light to your eyes. So, how does the light that causes earthshine on the Moon get from the Sun to Earth to the Moon and then back to Earth? Yikes! This is some path. No wonder it is a faint light by the time it gets back to you, the observer on Earth. For details on the path of this light, see ASTRONOMY:EARTHSHINE