Oh....

"Tuning" is when someone changes the factory software in the DME (or DDE for diesels) to change the way fuel, timing, boost, etc is controlled- ideally they 'optimize' this for the very best performance. (Hence "tune"). Often times this removes limits on torque/hp and boost, so you get significantly higher perforamnce. (It is MUCH less effective on normally aspirated cars)

The "software update" on Idrive is for the infotainment system, AFAIK. I am actually unaware of any updates released by BMW for this method.