Placing a nested report in another report – PB Docs 2018

When you place a nested report in another report, the two reports
can be independent of each other, or they can be related in the database
sense by sharing some common data such as a customer number or a
department number. If the reports are related, you need to do some extra
things to both the base report and the related nested report.

Usually, when you place a report within a report rather than
create a composite report, you want to relate the reports. Those
instructions are first.