Hierarchies order existing columns into a drill path. A product path might go from Category to Subcategory to Product. It doesn't change the underlying rows. A group combines selected members into a named category, while a bin divides a numeric column into intervals of a fixed size.
These choices have different consequences. A group that lists Bikes and Camping can collect the remaining categories into Other or leave their labels ungrouped. A price bin groups product list prices; it doesn't bin aggregated sales totals. Name the new field so a reader can tell which definition you used. Then put that field on a visual and inspect both the grouped members and the values outside the named groups.