If the belowThis argument is omitted then the command lowers $widget so that it is below all of its siblings in the stacking order (it will be obscured by any siblings that overlap it and will not obscure any siblings). If belowThis is specified then it must be the path name of a window that is either a sibling of $widget or the descendant of a sibling of $widget. In this case the lower command will insert $widget into the stacking order just below belowThis (or the ancestor of belowThis that is a sibling of $widget); this could end up either raising or lowering $widget.