Modal window

In user interface design, a modal window ( often called an "extended drop down menu" ) is a graphical control element subordinate to an application's main window. It creates a mode where the main window can't be used. The modal window is a child window that requires users to interact with it before it can return to operating the parent application, thus preventing the workflow on the application main window. Modal windows are often called heavy windows or modal dialogs because the window is often used to display a dialog box.