See, in order for an object to be a planet, it must be the one dominating it’s orbit and have no other bodies of comparable size under it’s gravitational pull, exceptions being the planet’s own moon. For example, in Earth’s orbit, there are no other objects in it besides the moon, which is pulled in by its gravitational pull. Therefore, it’s the dominant object in it’s orbit.
Though Pluto has a moon, there are other objects in it’s orbit that are not being pulled in by its gravitational pull. Pluto shares its orbit with objects from the Kuiper Belt (a very large asteroid belt), mainly rocks, ice and metal, AND two other dwarf planets, Haumea and Makemake. They do not orbit around Pluto like a moon, they just float along with the planet within it’s orbit.
And since Pluto passed two of the three conditions to become a planet, it’s not an “official” planet, but instead a dwarf planet. So it’s a planet, but it’s not a PLANET planet because it shares its orbit with other objects that are not being pulled into its gravitational pull, preventing it from being the dominant object in its orbit around the sun.
So basically it’s just a mini version of a planet with compulsive hording issues.