Types of UML diagrams – Unified Modeling Language (UML) is a standardized general-purpose modelling language in the field of object-oriented software engineering. UML includes a set of graphic notation techniques to create visual models of object-oriented software systems. UML combines techniques from data modelling, business modelling, object modelling, and component modelling and can be used throughout the software development life-cycle. It let developers and customers view a software system from a different perspective and in varying degrees of abstraction.
Below are the types of UML diagrams :
1. Use Case Diagram

A use case is a set of scenarios that describing an interaction between a user and a system. A use case diagram displays the relationship between actors and use cases. The two main components of a use case diagram are use cases and actors. It describes the functionality provided by a system in terms of actors, their goals represented as use cases, and any dependencies among those use cases.
2. Sequence Diagram




It shows how objects communicate with each other in terms of a sequence of messages and indicates the lifespans of objects relative to those messages. Sequence diagrams demonstrate the behavior of objects in a use case by describing the objects and the messages they pass. the diagrams are read left to right and descending.
3. Activity Diagram




Activity diagrams describe the workflow behaviour of a system. The diagrams describe the state of activities by showing the sequence of activities performed. Activity diagrams can show activities that are conditional or parallel. The main reason to use activity diagrams is to model the workflow behind the system being designed. Activity Diagrams are useful for analyzing a use case by describing what actions need to take place and when they should occur, describing a complicated sequential algorithm, and modeling applications with parallel processes.