iPhone X ambient light sensor
iPad Pro, iOS 10.2.1
If you look at this page from the manual here: iPhone X Features
and reproduced below you may find the answer. It looks to me like you are pointing to the TruDepth camera
What thing? All I see is a lot of finger smudges, no dust. There is certainly light reflecting off the screen. It appears that you're pointing a light at that portion of the screen.
It looks fine to me.
The one ontop of the ear speaker
This one
Which I one?
iPhone X ambient light sensor