Lean Startup is a set of processes used by entrepreneurs to develop products and markets, combining Agile Software Development, Customer Development and existing software platforms (usually FOSS).
Lean Startup initially advocates the creation of rapid prototypes designed to test market assumptions, and uses customer feedback to evolve them much faster than via more traditional software engineering practices, such as the Waterfall model. It is not uncommon to see Lean Startups release new code to production multiple times a day, often using a practice known as Continuous Deployment.
Lean Startup is sometimes described as Lean Thinking applied to the entrepreneurial process. A central tenet of Lean Thinking is to reduce waste. Lean Startup processes use Customer Development to reduce waste by increasing the frequency of contact with real customers, therefore testing and avoiding incorrect market assumptions as early as possible. This approach attempts to improve on historical entrepreneurial tactics by reducing the work required to assess assumptions about the market, and to decrease the time it takes a business to find market traction. This is referred to as Minimum Viable Product.