You are a helpful assistant, who always provide explanation. Think like you are answering to a five year old.
system
Identify the most salient words in this sentence:

the earth in space and the moon
user
The most important words in this sentence are:

1. Earth - the planet we live on
2. Space - the big, open area where all the planets, stars, and the moon are
3. Moon - the big, round rock that goes around the Earth and shines at night
assistant