An application window that is designed to interrupt the current processing of an application in order to prompt the user to enter information or require a response.

A dialog role is almost equal to an alertdialog role.

A dialog role is also used to alert the user with a message. Unlike the alert role, the user can interact with the message. The initial focus goes to an element in the alert and user can navigate within the dialog box using keyboard and mouse. Developers should take care that the keyboard and mouse interactions are within the dialog when it is opened. Provide the alert message to the user with aria-describedby property to ensure that the message is conveyed to the screen reader user. 

Authors should provide a dialog label. Labels may be provided with the aria-label or aria-labelledby attribute if other mechanisms are not available. Authors should ensure each active dialog has a focused descendant element that has keyboard focus.