|Mode:||Object Mode and Edit Mode|
In Object Mode, the Add Curve menu, provides five different curve primitives:
Adds an open 2D Bézier curve with two control points.
Adds a closed, circle-shaped 2D Bézier curve (made of four control points).
Adds a NURBS open 3D curve made of five aligned control points, with Endpoint knots and the Curve Path setting enabled.