Use the Tracking Gantt view to: 

1. View tasks graphically while still having access to detailed information about the tasks. (Tracking Gantt view)  
2. View tasks as rolled-up bars or milestones on their respective summary task bars, enabling you to see your whole project without losing sight of the tasks. (Bar, Milestone, and Milestone Date Rollup views)  
3. See how tasks progress across time and evaluate the slack and slippage between tasks. You can track progress by comparing planned and actual start and finish dates, and by checking the completion percentage of each task. 
4. Review changes made to tasks during levelling and the effects of resource leveling on task completion. 
5. See how tasks progress across time. Review progress by comparing planned (baseline) dates and actual start and finish dates, and by checking the progress of each task. 
6. See the baselines the project manager saved for the project.