It's just on and off.
However, when it's "off" and the car is on (i.e. I'm driving) you still get a little glow from the LEDs.
Some people get it and some don't is what I've been told, but it's because the LEDs require less power to run and that extra power that is there for the regular bulbs keeps them somewhat glowing.
That's another reason I want to swap out the LEDs in the map light.