Curve
...
Curve properties can be set on the Curves page of the Properties window.
Number of segments between adjacent control points: Curves are composed of many small line segments drawn between control points. A high number of segments will yield a smoother curve; a low number will make the curve appear more jointed. High number of segments
Low number of segments
Bezier Curve
Spline Curve
Bezier Curve Options: If the curve is a Bezier curve, the following options are available:
Show additional control points: Additional control points will be displayed when Edit Node mode is active (see Edit Tool and and Editing Splines and Bezier Curves). This also enables the Keep the Curve
Smooth option.
Regular control points in Edit Node mode
Additional control points in Edit Node mode
Keep the curve smooth: If checked, the additional control points at each node remain linear, so that no sharp corners can be created at a node. If not checked, you can move each additional node independently. Keep Curves Smooth - additional nodes remain linear
Keep Curves Smooth disabled
...