You draw open or closed splines to match the features of a clip that you want to warp or morph. Splines are drawn in a similar way as garbage masks, by clicking to add points, or by dragging to draw freehand segments.
You draw a spline around a feature at the start of an effect. When you add a spline, both a source and destination spline is added to the clip. Since these splines are initially linked together and overlap, your manipulations to the source spline affect the destination spline in the same way. After you have drawn and animated the source spline, you can unlink the splines and edit the vertices and tangents of the destination spline independently.
When creating a morph between two clips, you draw splines on the Input1 clip, then optionally copy them to the Input2 clip. When you link the splines, those copied to the Input2 clip become the destination for splines drawn on the Input1 clip.
You can show or hide source and destination splines, as well as change their colours.
