Set identifiers in QlikView Introduction
Set identifiers define the relationship between the set expression and the field values or expression that is being evaluated.
1: Represents the full set of all the records in the application
$: Represents the records of the current selection.
$N: Selections from the Back stack
$_N: Selections from the Forward stack
bookmark_id | bookmark_name: Server and app bookmarks can be used as set identifiers. Either the bookmark ID or the bookmark name can be used.