Gantt chart and its Timescale as a reference shows when activities have to take place, bars show the calculated values. If no progress has taken place, given (planned) and expected values are the same. As you start to insert actual values, bars will show progress based upon expected (actual) values.
Have a look at the small sample project, both activities have the same Given Earliest Start value, second activity got actual value, Gantt bar start and Given Earliest Start differ accordingly.
To review planned values versus calculated expected values use view
Work Breakdown > Plan/Actual Comparison (Time)