A lunar eclipse happens when the earth comes between the sun and the moon, so that the moon moves into the earths shadow. We see the moon because it reflects sun light back down to earth. If the earth is blocking that light then we can’t see it as well.
A lunar eclipse is where the moon goes behind the earth, with respect to the sun. In other words, when the earth’s shadow falls on the moon, it goes dark.
Often the colour of the moon changes too. This is due to some colours of light scattering through the earth’s atmosphere to shine on the moon. This means although it is a lot darker, it can still be seen (and often with a reddish hue).
A lunar eclipse occurs when the moon passes behind the Earth so that the earth blocks the sun’s rays from striking the moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a full moon.