What does the moon often mean in ancient poetry?

In ancient poems, the moon and moonlight are often used to express feelings.

For example, Li Bai's Thoughts on a Quiet Night: "There is such bright light at the foot of my bed, is there already frost?" Looking up, I found that it was moonlight, sinking again, and I suddenly thought of home. " .

I miss my friends at this moment.

In addition, it is often used to repose, such as:

Until, holding up my cup, I asked the bright moon to bring me my shadow and let the three of us. Invite the moon without wine.

Li Yuyue is like a hook, and the solitary phoenix tree locks the deep courtyard in autumn.