This is a poem by Tang Dynasty poet 李白 in my grade-7 语文 textbook:
《闻王昌龄左迁龙标遥有此寄》,李白
杨花落尽子规啼,
闻道龙标过五溪。
我寄愁心与明月,
随风直到夜郎西。
From what I understand, the poem laments how 李白's friend 王昌龄 has been 左迁 = 降职 = demoted and sent to 龙标 in Hunan province (away from 李白).
杨花落尽子规啼: here 杨花 refers to 柳絮 (images): willow seeds which cluster together during certain seasons in China; 落 refers to them falling, and 尽 refers to them being "used up"---so they've basically all fallen now; and 子规啼 refers to the cuckoo's (杜鹃) sound. This first part seems to indicate how or when 李白 learned of 王昌龄's travels (although I'm not sure; maybe it just refers to time elapsing).
闻道龙标过五溪: here 闻道 means something like "learned of"; my book says 龙标 refers to his friend 王昌龄, but the custom at the time was to refer to officials by where they are stationed, in this case 龙标; and 过五溪 refers to 王昌龄 going to 五溪, a region of west Hunan and east Guizhou where five rivers meet. So this line refers to 李白 learning of his friend being stationed elsewhere.
我寄愁心与明月: here 我寄 literally means "I send", although I'm accustomed to this referring to posting things by mail, but maybe it should be non-literally interpreted; here 愁心 means "my worries" and 明月 means "bright moon" (maybe a bright moon makes travel safer). I'm a bit confused about this line.
随风直到夜郎西: here 随风 (or 随君 in my textbook), which I think means "愁心与明月 travels with the wind"; and 夜郎西 seems to be another name for where 龙标 is going.
So maybe I'd translate it to:
The willow seeds have fallen, the cuckoo crows,
I learned Wang Changling has gone to the five creeks,
I send my worries and a bright moon,
On the wind, to west Yelang.
Question: How is my understanding of 李白’s poem 《闻王昌龄左迁龙标遥有此寄》?