What does the tree at the sow's meeting mean?

At the sow meeting, the tree means impossible. Just like ancient men and women wrote letters to show their loyalty to love.

I want to know you, and I will live long. There are no tombs in the mountains and rivers, Lei Zhen in winter and rain and snow in summer. Heaven and earth are close together, and I dare to die with you! It means the same thing! They all set off what they said before with impossibility.