The document discusses UML (Unified Modeling Language), which is a standard modeling language used to visualize, specify, construct, and document software systems. It describes the 13 official UML diagram types and how UML can be used in different modes like sketching, blueprinting, or as a programming language. It also discusses the history and development of UML and the Rational Unified Process (RUP) iterative development framework often used with UML.