Six Sigma is a methodology that companies use to reduce defects in processes and improve quality. It involves defining, measuring, analyzing, improving, and controlling processes to achieve a goal of 3.4 defects per million opportunities. Implementing Six Sigma involves establishing leadership commitment, forming a core team, providing training, defining goals and processes, identifying performance gaps, defining improvement projects, and establishing performance measures and incentives. The process flow includes establishing leadership and a core team, training, conducting periodic reviews, defining goals and current performance, identifying gaps, defining improvement projects, and creating an incentive system to drive implementation.