Control Points
Extrude Curve and Move
Reference
Mode:
Edit Mode
Shortcut:
E
Extrudes points by duplicating the selected points, which then can be moved, and connecting those points back to the original curve creating a continuous curve.
Tilt
Reference
Mode:
Edit Mode
Tool:
Toolbar ‣ Tilt
Shortcut:
Ctrl-T
This setting controls how the normals twist around each control point. The tilt will be interpolated from point to point (you can check it with the normals).
Clear Tilt
Reference
Mode:
Edit Mode
Shortcut:
Alt-T
You can also reset the tilt to its default value (i.e. perpendicular to the original curve plane).