From the press release:
Messenger Lite is under 10MB, so it’s fast to install and quick to start up. It includes Messenger’s core experiences such as messaging, sending and receiving photos and links, and receiving stickers... Messenger Lite is starting to roll out to people in Kenya, Tunisia, Malaysia, Sri Lanka and Venezuela. Look for Messenger Lite in other countries in the coming months.
I think the degree to which FB engrains accessibility in their products is admirable.