what is a lunar elcipse?

Answer 1

When the earth is directly between the moon and the sun, casting the shadow of the earth upon the surface of the moon.

Answer 2

The duration of the revolution of the moon around the earth and duration of the revolution of these two around the sun is different.This causes peculiar positioning of these two celestial bodis in such ways that the earth can cast its shadow on the moon(lunar eclipse)or the moon can block the sunlight(solar eclipse).Thus, during lunar eclipse, the sun,the moon.and the earth lie on a line with the earth lying in between the sun and the moon.In this position ,the earth's shadow falls on the moon.