This document discusses control charts, which were originally developed by Walter Shewhart in 1924 to distinguish between common and special causes of variation in processes. It provides background on Shewhart and the origins of control charts. The summary then explains that control charts can monitor characteristics measured on nominal, interval, or ratio scales using attributes or variables control charts. Attributes charts like c-charts and p-charts are used for categorical data, while variables charts like X-bar and R charts are used for continuous data. The document also discusses average run length and the performance of control charts.