The lunar eclipse is the situation that occurs when the earth comes in between the moon and the sun. When this happens, the rays coming from the sun becomes completely blocked. The new moon is one of the phases of the moon. When this happens, the moon is in between the sun and the earth.
It is true that for both situations, the moon is going to be dark, but the reason why they are dark will differ. Also, the lunar eclipse will also have a different look as compared to the new moon. You will know exactly what situation you are looking at when you check out the sky.