What do the leading words in ancient poetry mean?

The guiding word is the word that always guides the following poem.

For example, "Looking at the inside and outside of the Great Wall from a distance, I only feel boundless, and the river goes up and down, and I get lost." The last four sentences are all about "look", so "look" is the leading word. "Zi Ling" is the most common word in Liu Yong's ci, and the original intention of Liu Yong's ci is to sing with geisha.