The app uses the same branding as Facebook's mobile Messenger app, which received an update on both Android and iOS on Monday.
The app opens up two windows. One is a tall vertical window, which shows you who is online as well as Facebook's live feed, so you can see what your friends are commenting, posting and liking.
That window also shows you any friend requests, messages or notifications you may have.
The second window is for chatting, which shows you tabs for current conversations you may have going on.