As seen from the Moon, there are two bright objects in the solar system, the Sun and the Earth. When sunlight strikes the Moon's surface, we see the familiar phases of the Moon from the Earth. When Earth light strikes the Moon's surface, we see what is called earthshine. Just after sunset, if you look at the crescent Moon, or the half Moon, you will see the bright, sunlit portion of the Moon, but instead of seeing a black unlit portion, you will see it faintly lit. This is earthshine.