* The Kuiper Belt: This is a disk-shaped region beyond Neptune, extending from roughly 30 to 55 astronomical units (AU) from the Sun. The Kuiper Belt is home to many icy bodies, some of which are ejected into the inner solar system, becoming comets. These are known as short-period comets, which have orbital periods of less than 200 years.

* The Oort Cloud: This is a vast spherical cloud of icy debris surrounding the solar system, extending as far as 100,000 AU from the Sun. The Oort Cloud is thought to be the source of long-period comets, which have orbital periods of more than 200 years. These comets are thought to be perturbed by gravitational interactions with other stars or passing interstellar clouds.

So, the answer to your question is the Oort Cloud, though it's important to note that some comets may originate from the Kuiper Belt as well.