Pluto revolves around the Sun in an orbit that is not exactly circular, much like the rest of the planets. Rather, its orbit is more of an oval or egg shape. Because of this, Pluto will orbit inside of Neptune's orbit.
Discovered in 1930, Pluto is the second closest dwarf planet to the Sun and was at one point classified as the ninth planet. Pluto is the largest dwarf planet but only the second most massive, with Eris being the most massive.