What is the "W" light on my keyboard?

Since r/keyboards is pretty much dead i figured i'd try my luck here.. I own a steelseries apex 100 and on it is 4 LEDs. 1. "n" (number lock) 2. "c" (caps lock) 3. "s" (scroll lock) 4. "w" (???)

i've tried before to figure out what w is so i could mess around with the LEDs but i never found it. Suddenly, its on and I dont know how to turn it off.

halp.

EDIT: turns out r/keyboards is pretty active so i'll ask there too EDIT 2: my windows key doesnt work so the "w" might be for windows