Basics of UML:

In the field of software engineering, the Unified Modeling Language (UML) is a standardized specification language for object modeling. UML is a general-purpose modeling language that includes a graphical notation used to create an abstract model of a system, referred to as a UML model.
UML diagrams represent three different views of a system model:
Functional requirements view
Emphasizes the functional requirements of the system from the user's point of view.
Includes use case diagrams.
Static structural view
Emphasizes the static structure of the system using objects, attributes, operations, and relationships.
Includes class diagrams and composite structure diagrams.
Dynamic behavior view
Emphasizes the dynamic behavior of the system by showing collaborations among objects and changes to the internal states of objects.
Includes sequence diagrams, activity diagrams and state machine diagrams.
There are 13 different types of diagrams in UML.
Structure diagrams emphasize what things must be in the system being modeled:
• Class diagram
• Component diagram
• Composite structure diagram
• Deployment diagram
• Object diagram
• Package diagram
Behavior diagrams emphasize what must happen in the system being modeled:
• Activity diagram
• State Machine diagram
• Use case diagram
Interaction diagrams, a subset of behavior diagrams, emphasize the flow of control and data among the things in the system being modeled:
• Communication diagram
• Interaction overview diagram
• Sequence diagram
• UML Timing Diagram
UML is not restricted to modeling software. UML is also used for business process modeling, systems engineering modeling and representing organizational structures.