Look up at the night sky. The brightest thing you can see there is usually the Moon. The Moon is Earth's neighbor in space. It travels around the Earth, and one trip takes about 27 days.
The Moon does not make its own light. It is like a big mirror: the light of the Sun shines on it, and we see that light. That is why the Moon seems to change its shape. Sometimes we see a full circle, sometimes half, and sometimes only a thin line.
There is no air and no water on the Moon, so nothing can live there. In 1969, two American astronauts, Neil Armstrong and Buzz Aldrin, walked on the Moon. Their footprints are still there, because there is no wind to blow them away.