Assets rarely exist as standalone objects. More often, assets exist as part of a hierarchy in a "parent-child" relationship. The parent is always the original asset that was ingested (also referred to as the "source asset"). When some actions are carried out against an asset (e.g. transcode), new "child" assets are created. When child assets are created they are automatically associated to the parent asset as a child asset. The asset hierarchy provides a powerful means of traversing a tree of assets and understanding how they relate to one another.
Asset hierarchies are automatically created by the system when new assets are created. Users cannot create their own hierarchies.