Levels are used with dimensions to create a hierarchy.
The elements of a dimension can be organized as a hierarchy—a set of parent-child relationships, where a parent member summarizes its children.
For example, cities are the members of regions; products typically are part of product groups, and individual expense items are grouped into types of expenditure.
Levels of data range from the most summarized (up) to the most detailed (down).
Each level represents a different group within the same dimension. For example, a time dimension can include levels such as years, months, and days.
You can define a hierarchy level and add levels.