This document discusses Lean UX and its principles. Some key points covered include: - Lean UX applies Agile development theories and the Lean Startup methodology to UX design. - Its principles include developing an minimum viable product quickly through short development cycles, validating assumptions with customers early and often, and incorporating customer feedback to continuously improve the product. - It emphasizes failing fast through iterative testing of hypotheses to determine what customers want in order to build the right product.