Was bedeutet nSubItem in CListCtrl::InsertColumn(...)

int CListCtrl::InsertColumn( int nCol, const LVCOLUMN* pColumn );
int CListCtrl::InsertColumn( int nCol, LPCTSTR lpszColumnHeading, int nFormat = LVCFMT_LEFT, int nWidth = -1, int nSubItem = -1 );

Return Value:
The index of the new column if successful or -1 otherwise.

Parameters:
nCol:                The index of the new column.
pColumn:             Address of an LVCOLUMN structure that contains the attributes of the new column.
lpszColumnHeading:   Address of a string containing the column’s heading.
nFormat:             Alignment of the column. It can be one of these values:
                     LVCFMT_LEFT, LVCFMT_RIGHT, or LVCFMT_CENTER.
nWidth:              Width of the column, in pixels.
                     If this parameter is -1, the column width is not set.
nSubItem:            Index of the subitem associated with the column.
                     If this parameter is -1, no subitem is associatied with the column.

Wofür steht nSubItem bei einer Spaltenüberschrift ganz genau, kann damit nichts anfangen?