It's easy to make hierarchies to make drill-down operations.
A hierarchy will be formed when you drop a field on another field.
Deleting any member from the hierarchy would delete the actual field.
You can duplicate the field used in the hierarchy to use it as a non-hierarchial field for some calculation or visuals.
The hierarchy order can be changed as per user.
In the below image, there are not in hierarchy.
In below image, there are in hierarchy, where - indicates the hierarchy drill up and + indicate hierarchy drill down
Hope it helps you.