Pointer and Ownership References
A pointer is a reference that indicates usage, but not possession or responsibility, for another object. A pointer reference means that the object uses the other object in some way, and shares access to it.
An ownership reference means that an owner object is responsible for the objects for which it has an owner handle. Ownership references direct the writing of entire DWG and DXF files in a generic manner, such as beginning from a few key root objects.
An object can have any number of pointer references associated with it, but it can have only one owner.