root can be either a string (to specify a static path like /news) or a null or negative number to specify an ancestor of the current page (0 means current folder).
depth defines the tree depth.
Note: be careful, in Angular templates, inputs are considered as string unless they are interpolated, so root="/events" returns the string "/events" and it works. It is equivalent to [root]="'/events'".
But root="-1" is wrong, as it would return the string "-1" which is not a number. To get an actual number, interpolation is mandatory: [root]="-1".