The word spline I associate with wheels and curves with Bezier so I was surprised that in 3D modelling it is defined thus
“A spline is a Bezier-type curve that can be shaped and manipulated with a set number of control points, called CVs. Splines are used frequently in NURBS modeling, where a three dimensional mesh can be “lofted” between two or more splines to create a smooth surface.
Splines also have use in polygonal modeling and animation. In the former, polygons can be extruded along a spline with set number of segments extrusions such as these are a common technique for modeling any sort of tubular detail, including wires and pipes.
In animation, a spline can be used as a motion path.
Also Known As: NURBS curve, path.”
from http://3d.about.com/od/Glossary-S/g/Spline.htm Accessed 2/12/15
A fascinating history of curves is blogged here http://www.alatown.com/spline/
Diagram to show word derivation over years.