Interpolation is a method of constructing new data points within the range of a discrete set of known data points.
In motion control, the term interpolation is found in two places. Position interpolation refers to the generation of a path between two know points. This could be a simple linear interpolation or a more complex cubic spline interpolation as used by PMAC. The other type of interpolation is found when referring to sinusoidal encoders where it is used to generate very high resolution position feedback.