Rollups are special filters that only work with hierarchical parent/child components (that is, those in components with Tree Views). They are used in graphing, reporting, and list views, and are mostly used to produce high level counts of incidents, injuries, and so on. A rollup is a snapshot of the hierarchy at a particular time.

For example the number of incidents at a site - the parent site may have several child sites, and may also be part of a larger organization.