Psiphon Browser for iOS is a browser-only application and so will only tunnel data that is loaded in the app itself, and will not tunnel your other apps (like your Facebook or Twitter apps) through the Psiphon network. So, for example, if you wanted to use the Psiphon network to access your Facebook account, you would use Psiphon Browser to go the Facebook website. If you were to open your Facebook app, it would use your direct internet connection, and would not be tunneled through the Psiphon network.