Immersion, reading, usage of audio-visual cues, listening.
For immersion, you might be put in an environment that constantly uses the target language. This benefits the learner by allowing them to immerse themselves within the environment so they can practice using their target language skills. Games that use lots of speech to relay information to the gamer can especially help in this section.
Reading and reading fluency can also be improved by augmented reality. You have to read in the target language to understand the text given to you, or you might end up missing some vital information. The quicker you are able to read and understand the text, the better you are getting. This can also be backed up with games that allow their players to choose the verbal responses of the their character(s).
With any game, audio and visual cues are present always. The game helps by allowing the player to continue through the connection of key items and their descriptions. Take Pokémon Go for example. You want to catch Pokémon, which are represented by the Pokémon themselves. Or maybe the game wants you to find a Pokestop, which is marked by a Pokestop symbol. Listening to the audio also helps with the learner's ability to be able to listen, interpret, and respond quickly and correctly.