what does the title where the red fern grows represent?

The red fern represents the spirit of billy's dogs. It is based on a native american legend that says only an angel can plant the seeds of a red fern, which never dies, and makes the spot sacred.

it represents the bond between two a boy and his dog and that friendship will last forever.

According to the book- the red fern represents the strongest kind of love. The example given was according to Indian legend one winter there was a blizzard and a man and woman were lost in the woods. The next spring a red fern grew where the couple died... so the red fern represents the greatest possible love. And here it's the unconditional love a boy has for his pets.

Obviously, the red fern is a kind of memorial to the spirits of Billy's departed dogs. According to legend, an angel has to plant the seed of the red fern, and so wherever there is a red fern, it marks something very admirable and special. It is red, the color of blood, yet it is not a symbol of death. On the contrary, it helps Billy forget about the deaths of his dogs. Because an angel has honored his dogs, he understands that they are part of God's plans. His papa believes in fate, and when Billy sees the red fern, he is led to believe that there is a divine hand in what has happened to his dogs. He remembers that he prayed for the dogs and that all along, they seem to have been a gift of God. Perhaps this makes Billy accept that they were only a temporary gift. At least, it allows him to accept that their loss is part of a larger plan. So, the red fern helps Billy to understand that the death of his dogs is part of a bigger plan.