It's more like rotating on it's side. (tilted at close to 90 degrees), as compared with most other planets - which also is the case with Uranus.
(Venus however does rotate in the opposite direction to most planets.)
Pluto also orbits well away from the plane of the solar system which the other planets are close to.
It's generally thought that these anomolies result from gravitational interactions and possibly collisions of early planetary bodies before things settled down into the pattern we have today.
There probably were additional large bodies in the earliest times of the solar system's formation, and a collision of one of these with Earth is the most widely accepted theory of how the Earth acquired a single Moon which is relatively very large compared with other planets which have multiple much smaller moons.