MessageDialogs should be used to convey a message to the user. They must not interrupt the user's interaction with the application. They should include a message and one of the following button arrangements:
OK
OK Help
OK Cancel
OK Cancel Help
Yes No
Yes No Help
Yes No Cancel
Yes No Cancel Help
Cancel
Cancel Help
Retry Cancel
Retry Cancel Help
There are a number of different types of MessageDialogs: ErrorDialog, InformationDialog, QuestionDialog, WorkingDialog, and WarningDialog.
For more information, see the reference pages for DialogBox, ErrorDialog, InformationDialog, QuestionDialog, WorkingDialog, and WarningDialog.