Here's why:

* Spherical Body: Planets are large enough for their gravity to pull them into a roughly spherical shape.

* Orbits the Sun: Planets are celestial bodies that orbit a star, in this case, our Sun.

* Shares its orbit with other bodies: Planets often share their orbits with other bodies like asteroids, comets, and even other planets (in the case of Jupiter's Trojan asteroids).

While you might think of "sharing an orbit" as implying the bodies are constantly close together, it's more about sharing the same orbital path around the Sun. These bodies are often spaced out, but follow a similar trajectory.