This is NOT official Facebook application, and it's not developed by Facebook! Inbox Messenger. Inbox Messenger Lite is both, Facebook and Messenger in one app. It's application with ability to chat, send emoticons, videos, images, browse news feed, comments. With your Facebook friends. In every moment you have access to your inbox with new messages.
You are able to get the .apk installer of Inbox Messenger Lite 6.1.5 free of charge and have a look at users' reviews on Droid Informer. This file size doesn't exceed 1 MB and the app runs flawlessly on Android 4.1 and higher. This application was checked for viruses and it was found 100% secure. Inbox Messenger Lite has been originally designed by BOMA Soft and it belongs to the Communication category.