Six Sigma is defined as a management philosophy and problem-solving methodology focused on reducing variation and eliminating defects. It uses a define-measure-analyze-improve-control (DMAIC) process. Key aspects of a Six Sigma organization include Champions who drive the initiative, Black Belts who lead projects, and Green Belts who assist. The goal is to achieve no more than 3.4 defects per million opportunities through rigorous data-driven analysis and process improvement.