When the moon, in its orbit around Earth, sails into the Earth's shadow,
that's just another way of saying that the moon is temporarily in a place
where the sun can't shine on it, because the Earth is in the way.
When that happens, there's nothing shining on the moon to light it up,
and it becomes dark ... possibly for a few hours, until it sails out of the
shadow and into the sunshine again.
If somebody down below happens to be looking at the moon, and sees
this happening, then he might say to the person next to him "Oh ! Look
look look ! There's a 'Lunar Eclipse' going on !" A person who's not
looking has no idea that anything is happening, because a Lunar Eclipse
has no effect whatsoever on anybody (unless they're trying to walk along
a trail in the woods by moonlight).
All of this this can only happen at the time of Full Moon. So anybody
in any place where it's night time can see it happen (if his sky is clear).
That would be any place on roughly half of the Earth.
