What is the significance of horseshoe?

The significance of a horseshoe is to protect the horse's hoofs from being damaged. ie. Splitting of the hoof, cracking, lodged debris such as pebbles, rocks, feces, and other items that may injure the horse in the long run if inside of the hoof (not where the natural groove is, but INSIDE the hoof. Imagine a splinter inside of your fingernail, that's how I imagine how much it would hurt).