Eco Light/Setting

I did a search and read a couple of posts about the Eco setting in the Forte. Most of the other threads talked about how to turn it on/off. First, someone said that only the Koup SX trims have this setting to turn it on or off .. But mine's an EX Koup and I can turn it on and off, so I guess that "SX only" thing isn't true. Anyways, my main question though is what's the use of it?

I mean, does it make the care drive differently? More fuel efficiently? I never notice a difference in the way my car drives when I have it off or on. But not only that, when I do have it on, the indicator light will go on and off randomly. Like when I accelerate it turns off, and when I stay at a certain speed then it'll turn back on. My only thought was maybe the light just turns on to kinda "train" (for lack of better term) you how to drive more fuel efficiently and it shows you when you are. That's probably a stupid assumption, but I couldn't think of anything else lol. So what exactly DOES it do?