I recall reading about it in the owner's manual. IIRC, you can get to it anytime by holding the HV button down. And yes, it is a more aggressive use of the gas engine to both drive the car and charge the battery, not just drive the car. So the motor will continue running while the car is otherwise idle where the normal HV mode will switch to EV while at stop lights. Not sure why one would choose that option unless you have zones that are EV only and you need to be certain to have enough battery charge when you get there to go in, do your driving, and get out all on EV. I think I read somewhere they have some of those in Europe or they are in the works to do something like that? But if that were the intention, I would think there would also be a setting where you could force it to only use EV.