All of the major planets orbit relatively close to the same parallel plane, but not exactly on it.

We usually compare other things orbiting the sun to the ecliptic, which is the fancy name for the plane of Earth's orbit. Most of the major planets are within 4° of the ecliptic, except Mercury which is at about 7°.

As for the dwarf planets; Ceres is about 10°, Pluto about 17°, and Eris is almost at 45° compared to the ecliptic, which is one of the reasons why it other Kuiper belt objects got recategorized.