I understand the basics of it but wonder what is the intelligence behind it. I think it takes into account the speed and how much force is put on the pedals. Depending on the mode it provides more or less assistance. By looking at it I still don't fully understand it.Its the drive assistance indicator, its a guide as to how much power is being applied at any time. Have a look a it when you are riding flat, it's probably low as you may not need much help, when you go uphill it could rise as you need more assistance.
I reckon there isn't a single standard how pedal assistance works and different vendors do it differently but in the case of Bosch it is a black box, right?