Null
A null, is an empty object, invisible in the final rendering, that groups together object that can be affected by a free transformation. A free transformation is one that is not limited to a single type of transformation (rotation or translation), nor is the transformation limited to a single axis or direction in the 3D world.
In the Shaper interface, a null is represented by an intersection of axes.
A null object can be selected by clicking on it. The rotation and translation gizmos position and orient it in the world.