The theory is that a developer can estimate the approximate difficulty of a given task relative to other tasks and thus give a coarse estimate of how long a set

The theory is that a developer can estimate the approximate difficulty of a given task relative to other tasks and thus give a coarse estimate of how long a set of tasks will take. One is supposed to use this estimate, compare it against the amount of work actually accomplished in a given period, and then project ahead against estimates work remaining to get an idea of when the project will be finished. This is intended to help managers set expectations with customers and cut or adjust features if the date is too far into the future. Unfortunately, what most organizations actually do is use the progress estimates to try to bludgeon developers into working faster, with entirely predictable bad effects.