In a control vertex spline, the selected points define the vertices of the control frame. The control frame defines the shape of the spline. You can constrain and dimension the control points and frames. Control vertex splines provide a different method to create and modify splines. Control vertex splines are available in both 2D sketches and 3D sketches.
You can apply tangent, perpendicular, and smooth (G2) constraints anywhere along control vertex splines. For example, draw a line that is coincident to the control vertex spline but not at the end point of the spline. You can now apply a tangent constraint between the spline and the line, and to other geometry types besides lines.