^^ From what you found, which I think is from Wikipedia.
In short, the HICAS helps with turning.
From what I read, as you turn a corner while traveling over 80km/h the rear wheels will turn 1 full degree in the opposite direction in order to help the car turn "Better".
If you are not use to the HICAS, you will feel the rear 'kick out' abit.
Its just to assist you in turning at high speeds but a lot of ppl dont like it as it can be an annoyance, like I said you can feel the car kick or helping you to drive towards the turning direction and sometimes you might end up over steering.
I do believe they came standard on GTR's only.