In my experience there are three things that often get conflated around software estimates: 1 Effort versus calendar time. 2 Estimate versus commitment.

In my experience there are three things that often get conflated around software estimates: 1 Effort versus calendar time. 2 Estimate versus commitment. 3 Confidence level - are we talking P50? P99? P100 under some set of assumptions? I don't think I've ever worked in a setting where everyone shared the same understanding on all of these points.