Night mode is an automatic setting which takes advantage of the new wide-angle camera that's in the iPhone 11 and 11 Pro models. It's equipped with a larger sensor that is able to let in more light, allowing for brighter photos when the light is low.
16" MacBook Pro Now Available
Alleged iPhone XI and XI Max Molds Show Triple Camera Layout
These physical molds are presumably produced by case manufacturers based on leaked schematics to test early cases for the upcoming 2019 iPhones.
The front design is also shown on a Weibo post which may have been the original source for the images:
The square grouping of the triple-camera is consistent with other rumors and images that have leaked from the supply chain regarding Apple's upcoming iPhones.