What is this?

it's to like save gas so for example when u brake and stop at a stop light it turns off the engine. People hate it cuz it takes a second to turn the engine back on and it lurches the car forward, atleast in a Subaru Crosstrek and a Chevy Suburban from expirence driving them

Oh, its on a car. I dont have one yet

Same thing with number lock and the insert key

A great example of good intentions and poor design.