Dialog "forms" are either modal or modeless. Modal dialogs are the most common. A modal dialog changes the mode of input from the main application Form to the dialog. When you display a modal dialog you cannot switch between the dialog and another form of your program. Example: a Save dialog is modal, you either have to save a file or cancel the save, you can't do anything else in this program. Modeless dialogs are like a Find dialog. They stay on top but you can still do something in your main Form.