To start with, this is an unofficial app, it's an application that is not associated with Facebook in any way. This application can be considered a browser extension, it's a wrapper to the original Messenger application and tries to make it usable as a browser plug-in.

You can use it to talk to your friends from anywhere in the world, even without Internet access. It is very easy to use, just click on the icon to get connected. The App will automatically detect your current browser and let you continue using it.

You can use this app to share any type of file, from a photo, video or audio file to any application. However, keep in mind that you must have the permission to send that type of file.