A Block/Style Parent is closely related to a VIZBlock in that it is a compound object similar to a nested AutoCAD block. Just like the VIZBlock, it is used for organizing linked data from DWG files. When linking DWG data to 3ds Max, you need to decide how the incoming entities are to be organized in the scene. Objects in DWG files are commonly organized by layers, blocks, and entities, while 3ds Max scenes are organized by parent/child hierarchies of objects.
The main difference between a Block/Style Parent and a VIZBlock is that a Block/Style Parent allows for a parent/child hierarchy of “components,” but does not display any of its own geometry. A VIZBlock displays its own geometry and lists a set of “components,” or sub-objects.