The planets of the solar system all orbit the Sun more-or-less in a plane. Compared to the Earth's orbit, which defines the plane at zero degrees, the orbit with the largest angle is Mercury's whose inclination is 7 degrees (the angle of the orbit of the dwarf planet Pluto is 17. 2 degrees). The orbital characteristics of planets evolve as the protoplanetary disk of gas and dust dissipates, and as the young planets themselves migrate in the disk in response to their mutual gravitational influences and effects of material in the disk. Astronomers recognize therefore that the orbital appearance of a planetary system reflects its evolutionary story.
source https://phys.org/news/2021-10-orbital-flatness-planetary.html