A Class diagram is a visual representation of any system's objects and the relationships between those objects. When you open a Class diagram, the IDE displays a specific selection of icons in the Modeling Palette. A different set of icons is displayed when you open a Sequence Diagram.
When you change the name of a Class in your Class diagram, the change is propagated downward to any dependent, named elements of the old Class. Likewise, changing an operation's name or parameters in the Class diagram propagates the change to related Sequence diagram Messages.
In a Class diagram, Different fonts and styles are used to differentiate the types of properties, attributes, and operations in a Class: