To be Lean, in process improvement speak, is to maximize customer value by eliminating waste. This means that an organization can create more value for customers with fewer resources if they can understand customer value and focus key processes to continually improve.
The focus switch begins with management. In traditional business systems, managers tend to optimize separate assets and vertical departments, eliminating waste along isolated points. Managers who think Lean, on the other hand, optimize the flow of their products and services through entire value streams that run horizontally across assets and departments to the customers. Eliminating waste along value streams also creates processes that require less human effort, less capital, space, and less time to make products and services, thus enabling companies to better respond to customers with high-variety, high-quality, fast-throughput and low-cost solutions that continually improve. When combined with Six Sigma, a set of management techniques focused on eliminating variability, the Lean method is further buttressed, making obvious what adds value by reducing everything else (which does not).