Reference Operator
With this Node you can access an object using a relative search path. This path is described by the letters U, D, N and P. Use U and D to move up or down a hierarchy level respectively, and N and P to move to the next or previous element respectively. The Object Node also references objects in this way — see the description of the Object Node for more details.
This Reference Node finds the object that is directly below the Cube object (Path = D for Down), i.e., the Sphere object. Once found, the object (i.e. the Sphere) is then passed to an Object Node, which in turn outputs the object's name: Sphere.