Facebook messenger for iOS was initially released with basic features of messaging function taken from Facebook application. All you need to know is go to this page, download it free and login using same Facebook account. However, a new version 1.7 has been released which bring lots of new features in previous Facebook messenger.
Features which have been added in new version 1.7 includes an improved interface and ability to see when the other person is typing. In addition to that another important feature which is added in Facebook Messenger is that it shows the message sender when the reader actually reads the message with a read receipt.
I am sure now the application has become more attractive and certainly brings a lot of reason to download and use it frequently on both iOS and Android devices.