What is the significance of Kuiper Belt Objects?

Answer 1

They aren't usually very significant. The Kuiper belt is a region of space beyond the orbit of Neptune; we have discovered several small bodies, and there are doubtless millions more still smaller. Knowing virtually nothing about them, we can only speculate on what kind of objects they are, but they probably represent primordial material that was out at the fringes of the planetary nebula from which our solar system formed, 4.5+ billion years ago.

These might become terrifyingly significant in some later age, if something were to perturb one or more of these objects into orbits that would bring them into the inner solar system. But as of yet, they appear to pose no hazard.