What does the STABI control unit (switch)?

My stabi switch is in neutral position. It can be switch "ON" and "OFF".
Can you tell me what exactly this control unit do. I can't imagine the purpose of it, and i don`t want to use it before i know what it does. Why it must be "OFF" when offroading and "ON" on "good" road. What that`s mean? The explanation in the manual is not clear for me.

It disconnects the rear stabilizer/sway bar which allows the rear suspension to move more freely. From my experience it doesn't make a lot of difference.

Tony

Thank you Tony.
I will try it on and off the road today.