The UML is a design language that is the standard language that is used for software modeling and design. It was first developed by Grady Booch, Ivar Jacobson, and James Rumbaugh at Rational Software between 1994–1995. In 1997, the Object Management Group (OMG) adopted it as the standard language for modeling. Later, in 2005, the International Organization for Standardization (ISO) approved UML as an ISO standard, and since then, it has been adopted by every software community.
UML diagrams allow developers to convey software design to other people. It is a language that has a set of rules that encourages easy communication. If you learn to read UML, you can understand any software model that is written in UML. Explaining a software model in plain English would be very difficult.