I don't understand when the values for actual start and actual finish dates are determined, project updates the values of the Start Date and Finish Date fields to be the same as the "Actuals". Baseline Start and End Dates keep their baseline values at least though. Is there a way to change a setting or something so that Start and Finish based on the current plan, don't change to reflect "Actual" start and finish dates, or is this how it is supposed to work?
Yes, this is how the software works. Remember that this is the mantra of Microsoft Project: "Actuals always replace estimates." When you enter an Actual Start date, the Start date is changed to the Actual Start date. It works the same with the Actual Finish date as well. How does Microsoft Project remember the original Start and Finish dates? Those dates are stored in Baseline Start and Baseline Finish. When you apply the Tracking Gantt view, you can compare the Gantt bars of the original Baseline schedule (gray Gantt bars) with the current schedule (blue and red Gantt bars). Hope this helps.