This document provides an overview of data visualization. It discusses the goals of data visualization which are to communicate information from data in a clear and effective manner. Some key aspects covered include the history of data visualization from William Playfair's early graphs in the 18th century to modern tools. It also discusses important principles of data visualization such as maximizing the data-ink ratio and eliminating non-data ink as outlined by Edward Tufte. Examples are provided to illustrate good and bad design practices. Overall, the document serves as a high-level introduction to data visualization, its history, principles and examples.