Kore 2 basically allowed you to layer and route instruments/FX.
It contained the engines for all the NI instruments so they could sell a Kore Pack that, say, layered Kontakt with Absynth and then processed it with Guitar Rig. If you bought the HW controller, it basically had macro knobs and buttons. The Kore Player is for use with Kore Packs.
If you owned Kore 2 and the underlying instruments you could edit the stuff and create your own routings. It also hosted 3rd party VST/VSTi's. It allows you to do pretty much anything in terms of routing - one of my own favorites takes a simple delay and lets me insert any VST's I want into the feedback loop.