A lunar eclipse occurs when the earth comes between the sun and the moon and casts its shadow on the moon.
On the full moon night, the moon rises in the east after the sun sets in the west.
On such a night, the sun and moon are on the opposite sides of the earth.
A total lunar eclipse is visible when the moon is in the umbra region of the shadow of the earth, and a partial lunar eclipse is visible when the moon is in the penumbra region.