Transitioning from traditional Waterfall delivery to agile delivery involves many changes in the way we work. One fundamental change is the way we plan and forecast the completion of work. We shift from a heavy emphasis on work package-based, milestone-based estimations more towards capacity-based estimation underpinned by team velocity.
Even with the latter there is still a need to better understand time to complete work. Time matters to customers, workers and organisations even if we do not estimate work items in hours or days.  It helps us better understand our work and improve both quality and productivity.
Cycle Time is the time required to produce a part or complete a process, as timed by actual measurement.  A system of work to deliver value may comprise of many processes, each with their own cycle time.
Example: A waiter takes an order from a customer in a restaurant and passes the order on to the kitchen staff. The time to prepare the food involves one or more separate cycle times (different processes).
In the strictest sense, Lead Time is the time required for a product to move all the way through a process or a value stream from start to finish.  It is the entire duration to deliver value.
Example: A customer orders books from an online website. The Lead Time is from when the order is placed to when the customer has the books in their hands.
Productivity can be improved by removing waste from processes. Lead Time and Cycle Time analysis can provide us direction as to a) where to focus our attention for improvements, and b) where waste resides in an end-to-end process. By reducing waste in end-to-end delivery, costs can be reduced, customer experience can be enhanced, and it makes work more enjoyable for staff as common annoyances can be mitigated or eliminated.
Value stream maps are diagrams of every step involved in the material and information flows needed to bring a product from order to delivery.  These can relate to production-related related processes or design-related processes (concept to launch). 
As a basic introduction to value stream maps, common elements captured are:
Value stream maps differ from traditional process diagrams in that they capture performance data for the processes. Within a process we may capture data related to:
Having a greater level of quantitative information related to delivery times does not mean that we should stop using relative estimation methods. These insights will assist in providing more reliable estimates: