“Outside world” meaning outside of the US. The app has been available for a few months now on US soil – or those with an US iTunes account. I don’t see why they haven’t released it earlier because there were no issues at all using it outside the US at all. But now it’s “all good” and the app is available internationally for iOS and Android.
Get it if you’re using Facebook and are fed up by the regular Facebook app and only use the messaging part of Facebook. Screenshots of the app after the break.