Spline interpolation means connecting the frames with a smooth curve (no abrupt changes in value, slope or curvature, assuming that the degree of the splines is at least three). Linear interpolation means connecting the frames with line segments, so there will be abrupt changes in the slope, but the value will change continuously. Constant interpolation uses "horizontal" line segments to connect the frames, so the value will change abruptly. Sometimes spline interpolation will result in unwanted movement. For example, if you want to move a model in one direction, and then abruptly move it in another direction, spline interpolation will tend to "smooth out" the change of direction. A spline break at the transition frame provides a way of forcing the transition to be abrupt. A good way to learn how to use the animation palette is to remove any figures, and experiment with animating one or two simple objects, such as a ball and a torus. Try using one palette feature at a time, and observe the effect. Make sure that "skip frames" is off and "full tracking" is on, so that the results are easy to see.