The Curve function allows you to draw a four-point mathematically defined Bezier/Spline Curve in the Trace software.
The Bezier/Spline Curve is defined by four points: the Initial Position and the Terminating Position (which are called "Anchors") and two separate Middle Points (which are called "Handles"), which can be moved to alter the shape.
Splines are easier to handle in the software than Arcs for tangification and the conversion process when going to the Cut Preview.
Arcs are still provided in the software for those that prefer to draw with them, but the Convert Arc to Splines process will convert them to Splines for software simplification purposes.