The Estimated Start/End Dates are similar to Projected Dates with a few minor differences. One I think of at the top of my head is that if you have a "Must finish On", the Projected date equals that, but the estimated date continues to estimate the end date (meaning if you have a 2 week duration task, and your Must Finish On date is equal to 1 week from now but it is at 0% completion, the Projected Date will still be one week from now, but the estimated date will be 2 weeks from now. there are other minor differences, but I'm on vacation right now and don't have my notes! I'll see if I have more when I get back next week.