In the Sprint/Iteration Tracking phase, the agile team's focus shifts to daily execution. As each team member completes their assigned workitems, they update the current status of their work by entering actual and remaining to do effort. This allows the to team to get a very clear picture of the overall sprint status and monitor burndown. The idea is that the remaining effort required to complete the work should decrease as the sprint progresses.
If it appears that the remaining work will not approach zero by the end of the sprint, the team and/or management can take the appropriate measures (e.g., reduce the scope) to ensure success.
Typically, teams set up and use their own customized TeamRoom™ to drive and track their day-to-day work. Alternatively, they can use the Team > Detail Tracking option in the main menu for the same purpose, though they are less specific to the team.