Power Conditioning is the removal of EMF or RFI interference on the power line. This can be seen as 'garbage' on the sine wave.
Check out
this graphic to see what I mean.
The way Monster (and other products work) is they have the incoming wall AC go through an Isolation Transformer to give the electrical coming into the unit a clean sine wave clear of noise.
Then, each (set, usually) of outlets has their own Isolation Filter, so you wont get noise on the power inside the unit. An Isolation Filter is basically a very scaled down version of an Isolation Transformer.
Power BALANCING on the other hand, as the article states, is stepping up or down the incoming VOLTAGE to be exactly 120v, no matter the incoming signal (to an extent).