When the total lunar eclipse occurs what are the relative positions of the sun earth and moon

A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the sun, Earth and moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle.

The earth is between the sun and the moon

Explanation:

The Moon is non luminous that is doesn't generate light by itself so it depends on light from the sun so when its path through which it taps light from the sun is totally covered it means the Earth is closer to the moon than the Sun so that the Earth gets all off its light leaving nothing for the Moon and in this case the Moon is thrown to total darkness.