The Kuiper Belt is a doughnut-shaped region of icy bodies extending far beyond the orbit of Neptune. It is home to Pluto and Arrokoth. Both worlds were visited by NASA's New Horizons spacecraft. There may be millions of other icy worlds in the Kuiper Belt that were left over from the formation of our solar system. Scientists call these worlds Kuiper Belt objects (KBOs), or trans-Neptunian objects (TNOs). Trans-Neptunian objects are objects in our solar system that have an orbit beyond Neptune.
Similar to the asteroid belt, the Kuiper Belt is a region of leftovers from the solar system's early history. Like the asteroid belt, it has also been shaped by a giant planet, although it's more of a thick disk (like a donut) than a thin belt.
The Kuiper Belt shouldn't be confused with the Oort Cloud, which is a much more distant region of icy, comet-like bodies that surrounds the solar system, including the Kuiper Belt. Both the Oort Cloud and the Kuiper Belt are thought to be sources of comets.
The Kuiper Belt is truly a frontier in space – it's a place we're still just beginning to explore and our understanding is still evolving.