In many cases, Object names are referred to as being in 'slash' notation. This means that the full path to the Object is specified via slashes where / represents the top or 'root' level.
For example, consider that a main Movie contains a Sprite s1 and that Sprite (s1) contains another Sprite s2.
The full slash notation name of s2 is "/s1/s2".
This is also defined by the _target property.
Therefore,
_root.s1.s2._target would return the string "/s1/s2".