Announced earlier this year, the PlayStation App will serve a few different roles. It can turn your iOS or Android device into a game controller. It can act as a second screen for certain titles to mimic or expand the action from your console. And it can serve as a conduit onto Sony's PlayStation Network.
Via the PlayStation Network, you can use the app to watch what other people are playing and buy games that are downloaded directly to your console. You can accept invitations from other gamers to join in on the gameplay. The PlayStation App also provides a chat feature and can tap into Facebook and Twitter.