UML - Class diagram.

 - The class diagram is a Static diagram.
 - Visualizing, documenting and describing different aspect of a system.
 - Shows collection of classes, interfaces, associations, collaboration and constrains.

Purpose.

 - Analysis and design of the state view of an application.
 - Describe responsiblities of a system.
 - Base for component and deployment diagrams.
 - Forward and reverse engineering.

Type of Uml diagrams.

 - Structural Diagram.
 - Class Diagram.
 - Object Diagram.
 - Component Diagram.
 - Deployment Diagram.
 - Behavior Diagram.
 - Use case diagram.
 - Sequence Diagram.
 - Collaboration Diagram.
 - Statechart Diagram.
 - Activity Diagram.

http://www.tutorialspoint.com/uml/uml_class_diagram.htm