believe there are too many already talking about the definition "Lean". Therefore, I would not talk much anymore on this. You can find more resource about lean on the right side bar here or just listen to James P. Wormack in his audio book on "The Machine that Changed the World: The Story of Lean Production".
So if I would short it, I would like to make it P2F "People - Pull - Flow" which is "Respect people" "Use pull system rather than push" "Smoothen the flow". However according to Prof. Hines, the often forget is "Mura" which mean "overburden to human effort" and "Murai" which mean "uneveness or variation" of input. To me, if you are truly respect for the "people" you likely to solve problem of human effort exhaustion and the application of Six Sigma methodology could lead to eliminate of "variation" on 4Ms "Men, Methods, Materials, Machines".
At this point plus your further research on "LEAN" whether it is within manufacturing or service industry, I believe you already excite about it and understand how can lean manufacturing/service can deliver the business bottom line.
So, my closing remark here "What is lean?" is to remember the "P2F+2M".
