For example, when you are using a program and you want to open a file, you use the File Open dialog box. In Microsoft Windows, when you right-click a file and choose Properties, you are presented with the Properties dialog box.
Tip: You can press the Esc key to cancel or close a dialog box.
Modal and modeless dialogs
A modal dialog temporarily locks you out of the rest of an application until it is closed. While a modal dialog box is open, it will always be the top window of the application — no other windows will be in front of it.
A modeless dialog allows you to use the rest of the application while it is open. It can be hidden by other application windows.
A document-modal dialog is used in modern versions of macOS X, and in some applications such as Opera. Instead of appearing in its own window, the dialog is presented as a "sheet" attached to the window. While it is open, a document-modal dialog locks the user out of the parent document window, but other document windows in the application can still be used. An example of a document-modal dialog is the "Save As" dialog in OSX's TextEdit application, shown below.