Nintendo's official Japanese customer service Twitter account throws up some wonderfully odd bits of advice and help from time to time, and today it's attempted to clear up any confusion over that odd little shape found just below the console's screen.
We wouldn't blame you if you hadn't really noticed it before - we knew it was there but hadn't really given it all that much thought before now - but you can see it highlighted in the image above. As some of you may already know, Nintendo explains that this is actually the sensor for the console's automatic brightness setting.
Essentially, when you have automatic brightness turned on, the sensor will check the surrounding brightness and adjust itself to meet your needs. Nintendo notes that if you cover that sensor with your finger (again, making sure that you have automatic brightness turned on), you should notice that the screen will become darker.
If you're interested in checking it out, you can turn on automatic brightness by heading to 'System Settings' on the Switch's main menu, going to the 'Screen Brightness' tab, and making sure that the feature is set to 'On'.
So there we are, an interesting fact for anyone who didn't know about the sensor before, and an admittedly odd reminder from Nintendo's official customer support for those who knew already. Right, as you were!