The Lean Startup methodology is an iterative process for building new companies, products, and services. You start with an idea—a hypothesis about a problem. You build a minimal viable version of the product to tackle the problem and launch it to your market. You measure everything that happens to it, get useful data, and learn from it. Based on the learning, you create a new hypothesis, and iterate—over and over again.
The faster you can go through this cycle, the faster you will learn and succeed. It’s about validated learning.