NodeID, Parent Node ID in Crystal Reports???

Why does each characteristic (coming from BEx) shows up as the following in Crystal Reports 2011.  What are these...how are these used and what is the benefit?   Do they need to be joined if you have two Bex in one CR 2011.

Sales Volume

Node ID
Parent Node ID

Member Unique Name

                2 Sales Volume

                5 Sales Volume

Thanks.