The designator children describes any direct child of the current note. The List returned gives all immediate children sorted in ascending $OutlineOrder.
This designator removes the contextual ambiguity of older usage of 'child' for both group and item scope usage. By comparison the child designator is always assumed to apply to item scope (i.e. one referenced container only).
As designators ignore map adornments, a container note with just adornments on it but child notes with evaluate as having a $ChildCount (the number of adornments) but no children (the number of notes).
See also—notes linking to here: