A dialog or dialog box is a type of window in a graphical user interface which prompts for user interaction.
Dialog boxes come in two main types, modal and modeless.
Modal dialog boxes are spawned by a particular window and block events to that window until the interaction between the dialog box and the user is complete.
Modeless dialog boxes do not block events to the main application windows and both may be used at the same time. A common example is a search dialog in a document editor application which may remain open while not actively searching for ease of access by the user.