Pokemon Go will soon get an update to its AR mode. Called AR+, the enhanced version uses Apple's ARKit augmented reality technology and will include special new features and exclusive bonuses.
Like Pokemon Go's existing AR mode, AR+ will be available when catching Pokemon and adds depth perception and scaling improvements. Pokemon will appear closer to their canonical size--so a Snorlax will appear much larger in the real-world environment than, say, an Oddish. On top of that, Pokemon will appear in more fixed locations, meaning you can move closer to, away from, and around them as if they were occupying a specific space nearby.
If you opt to use AR+, you'll also see gameplay benefits. Pokemon have awareness, meaning quick movement can startle them and cause them to flee. If you manage to get close enough without spooking it, you'll get the "expert handler" bonus, which nets you extra XP and stardust upon catching the Pokemon.
AR+ is compatible with the iPhone 6s and above, fifth generation iPads, and all iPad Pro models. It won't replace the regular AR mode and will instead be a separate option.
A previous update to Pokemon Go, which is available on all devices, introduced weather to the game. You also have the opportunity to catch the Gen 3 legendary Pokemon Groudon until January 15. Dozens of other Pokemon from the series' Gen 3 games, Ruby and Sapphire, were introduced in Pokemon Go following the recent update, with the remaining third-generation Pokemon to come at a later date.