Ok, forgive my total ignorance in this but, what is OBD II exactly?

I have a VW Polo III . Is there any parameter of the car that can be monitored/modified by some hack in the empeg sw? If so, how?

Thank you!

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= Taym =
MK2a #040103216 * 100Gb *All/Colors* Radio * 3.0a11 * Hijack = taympeg