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.
macOS Catalina Now Available
Apple iPhone Components? No Intel Chip.
Samsung Electronics (applications/video processor), Marvell (802.11), Infineon Technologies (baseband), Broadcom Corp. (touch screen controller), and Cambridge Silicon Radio (Bluetooth)
Of interest, the CPU of the iPhone was never explicitly mentioned by Apple, but Intel has flatly denied that it is producing the processor for the iPhone. Buzz around the Macworld floor has suggested that a Samsung ARM processor is at the heart of the device.