Mary & Tom Poppendieck adapted the principles from Lean Manufacturing:
In a nutshell, Lean says to relentlessly eliminate anything that isn’t adding Business value and only work on what we absolutely need to be doing at this moment in time.
Eliminating waste means eliminating useless meetings, tasks and documentation. But it also means eliminating time spent building what “we know” we’ll need in the future (things are constantly changing so we often end up not needing them – or if we do, we have to rework them because conditions and our understanding has changed by then)
Lean Product Development and Agile are complementary concepts that both strive to deliver more value, more efficiently to the customer.