If you have ever downloaded the facebook app the you might have been prompted by facebook to uneccesarily download the messenger app to send messages,
CONTENT AND LAYOUT-
messenger is availble to both ios and android devices, this is like the added neccesary accesory which you have to download if you want to send messages to your friends and family who are connected to you on facebook, layout is simple this being the official messenger app for facebook to view and send messages, app starts almost instant and appears as a new tab in the facebook app if the app is already installed to your device. layout is blue themed based and is same as colour guidelines from facebook.
FEATURES-
messenger has added features of video and voice calling over data and WiFi, it can now also switch as your default messaging app is permitted, colour scheme can be also changed as per the user for added functionality.
USABILTY-
I used the facebook app in the past days and I can assure you that even if the facebook app itself requires tremendous space on your device I see no need of adding an extra messenger for the app, even this app has the by default capabilty to auto start hence draining your battery in the background, it does not serves to be an app to be of extra 200mb space on your device. also it requires high speed data connection and is nearly obsolete for 2G networks, load times are high and efficiency for message delivery is not very reliable neither I believe that end to end encryption is, facebook is trying to implement more and more tailored ads which suddenly points that facebook can use your personal data for its data analysis, many reports have been leaked about facebook laundering with user data in the name of better experience, this is my self experience, hope it complies to others experience too.