https://www.polygon.com/2017/12/22/16808158/pokemon-go-ar-plus-mode

Pokémon Go’s AR+ mode, available exclusively for iOS 11-compatible devices, is a feature that sounds a lot more minimal than it is. But in practice, Pokémon Go’s enhanced augmented reality capabilities are a fun addition to catching Pokémon — as long as you don’t mind looking more than a little weird when using them in public.

AR+ mode makes use of Apple’s ARKit, which allows for more authentic, dynamic applications of the technology. After updating to the latest version of the game, a pop-up appears to alert players on iOS to the feature; it’s checked off by default if they don’t choose otherwise on the pop-up.