Six Sigma is a business management strategy, originally developed by Motorola, USA in 1986. Six Sigma became well known after Jack Welch made it a central focus of his business strategy at General Electric in 1995, and today it is widely used in many sectors of industry.
Six Sigma seeks to improve the quality of process outputs by identifying and removing the causes of defects (errors) and minimizing variability in manufacturing and business processes. It uses a set of quality management methods, including statistical methods, and creates a special infrastructure of people within the organization ("Black Belts", "Green Belts", etc.) who are experts in these methods. Each Six Sigma project carried out within an organization follows a defined sequence of steps and has quantified financial targets (cost reduction and/or profit increase).
In short, it is an organizational goal to strive for 0 defects through the use of standard deviation calculations with the objective of removing those elements of the production process that create defects/errors. It is believed that this, in turn, will improve the production process and not only improve revenues as a result of improved quality, but also due to less waste that may occur from defects, etc.