In lunar eclipses, the moon is what is reflecting light. The moon gets in the way of the suns light and casts a big shadow over the Earth. Depending on the position of the moon, the shadow that is cast on the Earth may be noticeable, but most often, the shadow is way too dim to see. When people say that there is going to be an eclipse, they try to look at the sun and see the shadow. You will not be able to see the eclipse, and it does a lot of harm to your eyes. The effect may not be right away, but the effect will show in the future. So, lunar eclipses are when the moon blocks the suns light and casts a shadow on the Earth.