What are the status leds its function?

I just was wondering; does anybody know what the function isof the status leds above the keyboard? And why there are models with 2, and models with 3 status leds?
I own a 8100Y 16GB model (non asian keyboard) which has two status leds. One always is on (blue), but I never seen the second one light up. What does this light do?

When looking for pictures of this LED I also found that there are models with 3 leds as wel. Anybody know why?
3 status leds. 1:? 2:? 3: ON

2 status leds. 1:? 2:ON

One of them is CapsLock status.

The third led is usually a warning to have the trackpad disconnected.
I do not know the necessary key combination (Fn + ???) to achieve it since it varies depending on each model

For example, in the SurBook it is Fn + Spacebar