What is UML ?

UML stands for ‘Unified Modeling Language’. That’s fine, but what exactly does it mean ? This is a programming language that is used for object-oriented software development. To organize program code more efficiently, programmers often create “objects” that are sets of structured data within programs. UML, which has been standardized by the Object Management Group (OMG), was designed for this purpose. The language has gained enough support that it has become a standard language for visualizing and constructing software programs. UML is a general-purpose notational language for specifying and visualizing complex software, especially large, object-oriented projects. UML builds on previous notational methods such as Booch, OMT, and OOSE.
However, UML is not restricted to modeling software. UML is also used for business process modeling, systems engineering modeling, and representing organizational structures. UML has been a catalyst for the evolution of model-driven technologies, which include Model Driven Development (MDD), Model Driven Engineering (MDE), and Model Driven Architecture (MDA). By establishing an industry consensus on a graphic notation to represent common concepts like classes, components, generalization, aggregation, and behaviors, UML has allowed software developers to concentrate more on design and architecture.
The Unified Modeling Language is an international standard:

ISO/IEC 19501:2005 Information technology — Open Distributed Processing — Unified Modeling Language (UML) Version 1.4.2.

The Unified Modeling Language (UML) first appeared in the 1990′s as an effort to select the best elements from the many modeling systems proposed at the time, and to combine them into a single coherent notation. It has since become the industry standard for software modeling and design, as well as the modeling of other processes in the scientific and business worlds. UML has matured significantly since UML 1.1. Several minor revisions (UML 1.3, 1.4, and 1.5) fixed shortcomings and bugs with the first version of UML, followed by the UML 2.0 major revision, which is the current OMG standard.
UML is a tool for specifying software systems and Standardized diagram types to help you describe and visually map a software system’s design and structure. Using UML it is possible to model just about any kind of application, both specifically and independently of a target platform. While UML is naturally oriented towards Object-Oriented programming, but it is just as easy to model procedural languages such as C, Visual Basic, Fortran etc.