Each motion-sensing controller includes an infrared (IR) camera at the bottom.
It doesnt look like a camera; there’s no traditional lens.
If you look, though, you’ll see the black spots at the bottom.

Gamespot YouTube video
What Can the Motion IR Camera Do, Exactly?
Its not far off from the way sonar works.
This allows the Joycon controllers to see objects and motion to use it as an input method.
The image detection is probably a lot better than you expect.
The IR sensor can also detect a heat map.
But, its not high quality or a very good camera.
You cant point your Joycon at something and snap a picture.
To take a screenshot, tap theCamerabutton on the left Joycon.
This instantly saves whats shown on screen.
From here, you’re able to view, delete, or filter your screenshots.
Its not exactly clear why this functionality is so limited, but it’s nailed down.
By default, the Switch won’t show any pictures or videos that arent screenshots from the Switch itself.