Eclipse of the Moon
Eclipse of the moon in Italy
An eclipse of the moon happens when the Earth gets between the sun and the moon, so the light from the sun can't get to the moon to be reflected towards the Earth. In other words, the shadow of the Earth covers the whole moon.
A total eclipse of the moon can only happen when the moon is full, because that's when the moon is exactly opposite from the sun in the sky. The moon is full about once a month, but eclipses happen less often because sometimes the moon is too high or too low for the Earth's shadow to fall on it. Usually lunar eclipses (eclipses of the moon) happen two to four times a year.
The moon and eclipses of the moon
Sometimes they are full eclipses, and sometimes only part of the moon is eclipsed. When there's an eclipse of the moon, anyone on the night side of Earth can see it.