Most organizations have a hierarchical structure in which departments (or other business units) report to one or more higher-level units. In a traditional organizational chart, the lower units on the chart typically report to increasingly higher units.
Microsoft Office PerformancePoint 2007 Management Reporter uses the term reporting unit for each box in an organizational chart. A reporting unit can be an individual department from the financial data, or it can be a higher-level, "summary" unit that combines information from other reporting units. For a report definition that includes a reporting tree, one report is generated for each reporting unit and at the summary level. All of these reports use the row and column definition that are specified in the report definition (unless the report definition specifies to use the reporting tree from the row definition).
Each reporting tree contains a group of reporting units. You can easily add or change reporting units without changing the financial data.