It seems that the software was intended for internal use only inadvertently shared with outsiders. After installing the application, you can directly chat with your online friends. To make the application to use it is true that you have to log onto the social network through a browser. If you are not logged in and click the "Register" button will automatically open the browser.
Options
You also see through the icons at the top, similar to those on the website, notifications, friend requests and messages. One-button bottom right, the application can be put down to the right of the screen like a toolbar. There is also a search field to quickly screen a friend to look in the list. Above the list of contacts you can see the famous Ticker face with recent activity of friends.
Once you start a conversation with a friend, a new window in which, through all open tabs calls are grouped. Facebook Messenger takes place in the system tray as shown below. By right clicking on the icon will have a number of options appear.
Update
A few hours after the leaking of the link to download the software, Facebook has decided to make an official release of it rather than get online.
Download Facebook Messenger for Windows can be done