UML Diagrams is Designed to let developers and customers view a software system From a difference Outlook.
unstable degrees of idea.

Use Case Diagram displays the relationship among actors and use cases.

Class Diagrams: models class structure and contents using design elements such as classes, packages and objects. It also displays relationships such as containment, inheritance, associations and others

Interaction Diagrams

State Diagram displays the sequences of states that an object of an interaction goes through during its life in response to received stimuli, together with its responses and actions.
Activity Diagram displays a special state diagram where most of the states are action states and most of the transitions are triggered by completion of the actions in the source states. This diagram focuses on flows driven by internal processing

Phisical Diagrams:

UML is not a method by itself; however, it was designed to be compatible with the leading object-oriented software development methods of its time (for example OMT, Booch, Objectory). Since UML has evolved, some of these methods have been recast to take advantage of the new notation (for example OMT), and new methods have been created based on UML. The best known is Rational Unified Process (RUP). There are many other UML-based methods like Abstraction Method, Dynamic Systems Development Method, and others, designed to provide more specific solutions, or achieve different objectives.