Hierarchies are a natural form of data organization. For example, you can break up any given time interval into intervals of shorter duration based on years, months, weeks, days, and so on. Similarly, the territory of United States consists of well-defined states, then counties, then municipalities and incorporated and unincorporated areas.
Arcadia Data allows you to define dimensional hierarchies, and then use them in visuals to enable a smooth transition between the hierarchical levels. In this manner, you can drill down towards an ever-increasing level of detail, or to abstract to a less granular level.