Answer:
The Project baseline is used for assessing performance, and improving the estimation accuracy (for the future). Having said that, the project baseline is excellent for the guiding the execution of the next project.
If you imagine your project plan is a boat race between Oxford and Cambridge. Your Boat is Oxford (the schedule what you have told your colleagues will happen) tracking allows you to create a second boat Cambridge which is what actually happened. Every task in your schedule is a boat with an alter ego boat to track what actually happened. You can see which tasks started and finished earlier or later than expected. This is called tracking the variance between the base line plan (the schedule you have set or announced and the actual outcome