The Properties window shows information about an item that is currently selected (in focus). The "in focus" element can be an element selected in the Model Tree window (or other windows), an element selected on the diagram, or even a diagram itself.
The Properties window also enables you to change the properties of the currently selected element or relationship. The available properties depend on the kind of the element that is selected. There are properties which are read-only and grayed out (such as "element kind") and properties that you can modify (for example, "name").
If an operation or property takes a parameter, you can quickly jump to the respective parameter type in the Model Tree window, directly from the Properties window. To do this, right-click the "type" property of the parameter in the Properties window and select Select in Model Tree from the context menu. The same is applicable for return parameters.
Changing a property of an element from the Properties window is immediately reflected in the diagram. Likewise, making a change in the diagram (for example, changing the visibility of an operation from public to private) affects the applicable property in the Properties window.
Properties that are enclosed within guillemets represent stereotypes (for example, «final»). You can add custom stereotypes to the project, in which case they would appear as properties in the Properties window, in addition to the default ones. For more information, see Example: Creating and Applying Stereotypes.