Forkcasting -- Types of estimates
Estimates like "we'll have it to you by 2024-Oct-01" are delivery date estimates. They're pinned to a specific date in the calendar and most often given to customers and used for sequencing "resources" (i.e. people). That is, if a staff engineer is expected to finish project A by a given date, then that's roughly when they can start work on project B.
These incorporate many sources of uncertainty, such as how long the work will take, who will be available to work on it, what projects are ahead of it in the queue, and so on.
This is closely related to the concept of "lead time", which is the duration between receiving the request and the customer getting the goods. This is effectively the lead time with a fixed start date, so I don't differentiate between the two.
An estimate like "this will take 5 days from start to finish" is a cycle time estimate. It's not pinned to a specific date in the calendar, and unlike lead time it ignores any spent waiting for someone to start work on it. it does not care that it'll take 2 devs to write it, 1 to review, and 1 to deploy it. Some tools offer this number directly as the duration between pulling a ticket into the InProgress state and Done state.
