the Prince was crying about his rose, and is talking with his new friend the fox.
The Prince is sad because he thought his rose was unique, but now knows better, because he has seen a row of rose bushes and many more roses. The fox explains that his rose is unique because of the relationship between them. That relationship is the bond of the heart, which cannot be seen by the eyes. With that bond come feelings of responsibility and love. These are some of the greatest bonds on the planet, and are completely invisible to the eye