A badge is a concise visual indication of something important to the user.
A badge is an unobtrusive notification in an application, indicating to the user a count of actionable objects that the user may wish to attend to. For example, number of new emails or unread messages.
A badge is not to be used as an urgent message requiring immediate user action, but rather assists in program flow, giving the user information about another part of the application that is not currently in focus.