All of sudden my keyboard on my MacBook Pro 2015 has started glowing. I don't know which key I turned on. Is there way to turn it off?
F5 decreases keyboard brightness, F6 increases it.
For more information see the Apple KB article Adjust the brightness of your backlit keyboard. If you don't like that the illumination automatically adapts, you can turn it off in System Preferences → Keyboard → Adjust keyboard brightness in low light.