The core idea behind Lean principles is to “maximize customer value while minimizing waste. Simply, lean means creating more value for customers with fewer resources.” (https://www.lean.org/WhatsLean/)
Lean is more than a collection of tools, it is a way of thinking about creating value, for the customer, while at the same time consuming the least possible resources.
An important term found in lean circles is the Japanese word muda. Muda means waste, “specifically any human activity which absorbs resources but creates no value: mistakes which require rectification, production of items no one wants so that inventories and remaindered goods pile up, processing steps which aren’t actually needed, movement of employees and transport of goods from one place to another without any purpose, groups of people in a downstream activity standing around waiting because an upstream activity has not delivered on time, and goods and services which don’t meet the needs of the customer.” P15, Lean Thinking: Banish Waste and Create Wealth in your Corporation, James P. Womack and Daniel T. Jones.