A report band that provides a functional copy of the source band below which it is located.
The following image illustrates the corresponding option in the context menu of an GUI.
After adding a sub-band to the collection, it provides a functional copy of the source band. A sub-band's behavior, as well as its position within the report band hierarchy, is dictated by the source band type.
By using sub-bands, it is possible to create multiple versions of a band within a single report (e.g., to choose an appropriate version later on based on a specific condition).
See Introduction to Banded Reports for more details.