You might need to expand on what you are asking,
The Parent in the Grid View is the single parent of the list item in the row. Every item rolls up to a parent (except the top level)
but, the parent hierarchy is the 'configure' tab, this allows you to connect a detailed list with a summary list (composite hierarchy), see the video in https://community.anaplan.com/anapedia/model-building/lists-and-roll-ups/general-lists
"The Parent Hierarchy indicates whether another list is going to be used for the next level 'up' from the list shown. In this model, Opportunities roll up into Sales Reps and Reps roll up into the Organization. The following video describes the uses and benefits of a parent hierarchy."