A progress report is a form that you complete and share with the rest of your team. Is shows what tasks you've been working on, how long you've been working on them, and how much more work you think remains to be done.
You should fill out a progress report every so often - every week or every day, whenever you complete a task, or at any interval that makes sense for you and your team. That way, everyone knows the current overall status of the project. After each progress report has been completed, PlanIt9 reschedules all of the remaining tasks and recomputes the final project completion date.