Tableau Exam Desktop-Specialist Topic 11 Question 58 Discussion

When you connect to a data source, Tableau automatically separates date fields into hierarchies so you can easily break down the viz. You can also create your own custom hierarchies. For example, if you have a set of fields named Region, State, and County, you can create a hierarchy from these fields so that you can quickly drill down between levels in the viz.

https://help.tableau.com/current/pro/desktop/en-us/qs_hierarchies.htm