Internally, assets are identified uniquely by their id. However, a numerical value is hardly useful for humans beings. Therefore stock may also be identified by two labels. The primary nametag (aka the asset type) and the variant tag (aka the asset subtype).
Labels are stored with assets by reference. This allows for centrally changing (or deleting) nametags. The important distinction between name and variant is that a name is mandatory and a variant is optional. Therefore, when deleting a name, all associated assets are deleted as well.