Messenger Lite is an official client developed by Facebook for its well-known instant messaging service. The biggest draw is that this client takes up much less space than the standard version, occupying a little less than 10 megabytes. This makes it lighter, which means it can run without any problems on older devices with previous versions of Android.
The application is an official one, so it has practically all the same functions as the original chat service, enabling you to talk with your friends individually or in groups by sending and receiving text, images, videos, and stickers.
The difference between this client and unofficial ones that you can find online is that Messenger Lite can work in the background and send notifications for messages from your friends, like triggering vibrations or lighting up the device's screen when there is any activity. In practical terms, it has the same features as the original client without taking up as much space and consuming as many resources, which is what Facebook applications are generally known for.
Messenger Lite is a fantastic alternative to the official Facebook client. It's especially useful in countries where wireless connections struggle with the huge amount of data needed to run the official client. It's also compatible with a large number of devices and older versions of Android (as far back as 2.3 Gingerbread), though of course you can use it no matter what your situation is.