Driving points are reference points that control the geometry of a dependent spline. Driving points are typically created automatically when free points are used to generate a line, curve, or spline.
When selected, driving points display 3D controls.
You create driving points from placed hosted points. See Placing Hosted Points along a Spline.
To place a driving point along a spline
The point is now a driving point and can be used to modify the geometry of the spline as needed.