When the Moon is not visible due to Earth's shadow, it's called a lunar eclipse.

Here's a breakdown:

* Lunar Eclipse: This occurs when the Earth passes directly between the Sun and the Moon, casting a shadow on the Moon.

* Types of Lunar Eclipses: There are three types:

* Total Lunar Eclipse: The entire Moon is within Earth's umbra (the darkest part of the shadow).

* Partial Lunar Eclipse: Only part of the Moon is within Earth's umbra.

* Penumbral Lunar Eclipse: The Moon passes through Earth's penumbra (the lighter, outer part of the shadow), resulting in a subtle dimming of the Moon's surface.