Facebook launches messenger for iphone and android. This messenger is standalone app in which you can chat and send messages to each other and tap on any message and continue to add messages. You can mute the notification of messages for e.g. till 8 am or you can mute the messages from some of your friend. As you know there are other apps available for facebook but they are full fledge facebook but now facebook has launched this app which only contain messages and chat and some little status updates and other features also.
As you have heard that facebook messages are just like beluga. Beluga was acquired by facebook in February. And now this messenger is also made on the same pattern of beluga format. Messenger team said that Beluga will keep running. You can now download this facebook app from apple App store or android market. Facebook uses same platform for updating messages and recent chats for this app and facebook website.
If you want to create group then the contacts from your facebook contacts and contacts on phone are used and  request are sent to all the people. If the people are in facebook then request is sent by facebook messages else the request is sent through sms. In a group you can also make a map where all the locations of your friends are shown. As there are millions of iphone and android and facebook users so this messenger by facebook will catch market and become more popular as it is from facebook.