Put simply, it combines CV signals in different ways. Any non-audio cable can patch into this device.
For example, you could put two different LFOs into its inputs and then output a CV wave that would be some sort of blend of the two LFOs - by averaging the values of the two inputs, or subtracting one from the other, or some other method of combining them. You could also do this with other CV sources, for instance, the Gate and Note CVs that come out of a Matrix.
So just as a theoretical idea, you could feed a Matrix' Note CV into one side, and one of the Sample/Hold LFOs from a Subtractor or Polar into the other side, and what would come out would be the notes from the Matrix moved up or down according to the LFO values and whichever combination method was selected. You send that to some synth's CV input, and get a constantly varying sequence of notes.