O.K., you asked for it.
It's on a Youtube video from AB and it is explained more clearly there, but from what I saw, it is a reset of engine ECU operating parameters back to factory default settings. They say it should be done after you replace things like the MAF, O2 sensors, etc, because the ECU adjusts to continuously degrading performance of various controllers (MAF, O2 sensors) until they get out of acceptable specs, then the dash light goes on. When you replace the worn-out/faulty item, the ECU still retains the degraded performance parameters and will run with those unless and until the ECU is set back to default specs.
I believe i have explained it fairly accurately. And if so, I suspect many, if not most D2's are running around with degraded performance even though bad parts have been replaced and the Adaptation Reset has not been performed, especially by the DYI crowd. So folks complain their D2 still runs like crap and give up on 'em.
I've not heard of this before yesterday when I started sniffing around the Net and ren across the AB Youtube upload.
It's under "iLAND Diagnostic App: Discovery Engine & Transmission Adaption Reset"
I could be completely off base, but this could clean up a whole lot of Disco2 issues from a whole lot of folks.