Used to flag records for insert / update / delete or reject based on condition.
Forward Rejected rows -
By default the rejected rows are forwarded to the next transformation.
All the rejected rows are written to the session reject file. If you disable this option then the records are written to session log file. If you enable row error handling then the rows are written to row error logs and not to the session log file.
Aggreagator after Update Transformation
If a record is flagged for delete, then the aggregator will subtract the value, if it is flagged for insert then it is added.