From Aspire 9 manual:
Rough Machining is used when carving 3D parts to clear away excess material when the part is too deep for the finishing tool to cut in a single pass.
Finish Machining is used to machine the final pass on the finished 3D part.
"final pass" suggests most of the model has already been cut.
Adding the note Randall suggested is obviously useful to make it totally clear, but nothing is really missing.
Roughing then finishing is a general practice in 3D machining, so it's not supposed to be detailed in the software manual.
But I think it should be added to Vectric's Intro-To-CNC-Vectric2013.pdf. This is a very good document, but this explanation is lacking and this 2 step process is not obvious for 3D CAM beginners.