In the terms of the Celestial Chorus, every Shard Realm is a fraction of the One. A Shard Realm is connected to one of the planets within the Solar system and form its own specific Umbra. Each Shard Realm is connected to a specific Sphere that is dominant within its boundaries. Every Shard Realm is also connected to a Shade Realm, which is rumored to lead into a parallel universe dominated by one of the Spheres. Each Shard Realm is inhabited and ruled by a powerful Celestine.
Modern terminology usually refers to the Shard Realm simply as the associated celestial body.