This document provides an overview of the Six Sigma methodology. It defines Six Sigma as both a quality management methodology that uses tools and theories to improve processes and reduce defects, as well as a statistical concept where higher sigma levels result in fewer defects. The goal of Six Sigma is to achieve near-perfect processes with 3.4 defects per million opportunities. It explains that Six Sigma systematically identifies problems, reduces errors and waste, and improves processes to increase quality and customer satisfaction while decreasing costs.