This is designed the reduce the annoying the glare from people who look at their phones during movie screenings.
The next iOS update for both iPhones and iPads will introduce a 'theatre mode' that will reduce the annoyance of someone checking their devices during film screenings.
According to
Sonny Dickson, who has correctly predicted many of Apple's new technologies, a popcorn-shaped icon will appear in the Control Center which will put the mode into operation.
https://twitter.com/SonnyDickson/status/814931454828412929?ref_src=twsrc%5Etfw
According to AppleInsider, it will "disable system sounds and haptic feedback, block incoming calls and messages and reduce initial screen brightness during a movie."
The update is due to roll out on iOS10.3, which should start loading on devices on 10 January.